Databridges Node.js server Library

DataBridges makes it easy for connected devices and applications to communicate with each other in realtime in an efficient, fast, reliable and trust-safe manner. Databridges Node.js client library allows you to easily add realtime capabilities to your applications in record time.

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We would love to see what you build on dataBridges platform. We are available at tech@optomate.io to answer all your queries.

https://www.databridges.io/developers.html

Usage Overview

The following topics are covered:
- Supported platforms
- Installation
- Initialization
- Global Configuration
- Required
- Optional
- Connection
- Objects
- object:ConnectionState
- Properties
- Bind to connectionstate events
- Functions
- object:Channel
- Subscribe to Channel
- Channel Information
- Publish to Channel
- Send Message to Members / sessionID
- Binding to events
- System events for channel object
- object: rpc (Remote Procedure Call)
- Initialize rpc Server
- Register rpc functions
- Register Server
- Unregister Server
- resetqueue()
- System events for rpc server registration.
- Server Information
- Connect to Server
- Execute Remote Procedure Call
- object:Cf (Client Function)
- Execute Client Functions
- Properties
- Rate Limit and Concurrent connection
- Change Log
- License

Supported platforms

Node.js version 10 or newer. (The current Long Term Support (LTS) release is an ideal starting point).

Installation

You can use NPM package manager to install the package.

``bash
npm install databridges-sio-server-lib --save
`

> Note : Databridges library uses socket.io for websocket protocol management.

Initialization

`js
const dBridges = require('databridges-sio-server-lib');
const dbridge = new dBridges();
`

Global Configuration

$3

The following is the list of required connection properties before connecting to dataBridges network.

`javascript
dbridge.auth_url = 'URL';
dbridge.appkey = 'APP_KEY';
dbridge.appsecret = 'APP_SECRET';
`

You need to replace URL , APP_KEY and APP_SECRET with the actual URL ,Application Key and Application Secret.

| Properties | Description | Exceptions |
| ----------- | ------------------------------------------------------------ | -------------------------------------------------------- |
| auth_url | (string) Authentication url from dataBridges dashboard. | source: DBLIB_CONNECT
code: INVALID_URL |
| appkey | (string) Application Key from dataBridges dashboard. | source: DBLIB_CONNECT
code: INVALID_AUTH_PARAM |
| appsecret | (string) Application Secret from dataBridges dashboard. | source: DBLIB_CONNECT
code: INVALID_AUTH_PARAM |

$3

The following is the list of optional connection properties before connecting to dataBridges network.

`javascript
dbridge.maxReconnectionRetries = 10;
dbridge.maxReconnectionDelay = 120000;
dbridge.minReconnectionDelay = 1000 + Math.random() * 4000;
dbridge.reconnectionDelayGrowFactor = 1.3;
dbridge.minUptime = 200 ;
dbridge.connectionTimeout = 10000;
dbridge.autoReconnect = true;
dbridge.cf.enable = false;
`

| Properties | Default | Description |
| ----------------------------- | ----------------------------- | ------------------------------------------------------------ |
| maxReconnectionDelay | 10 | (integer) The maximum delay between two reconnection attempts in seconds. |
| minReconnectionDelay | 1000 + Math.random() 4000 | (integer)* The initial delay before reconnection in milliseconds (affected by the reconnectionDelayGrowFactor value). |
| reconnectionDelayGrowFactor | 1.3 | (float) The randomization factor used when reconnecting (so that the clients do not reconnect at the exact same time after a server crash). |
| minUptime | 200 | (integer) Uptime before connected event is triggered, value in milliseconds. |
| connectionTimeout | 10000 | (integer) Number of milliseconds the library will wait for a connection to be established. If it fails it will emit a connection_error event. |
| maxReconnectionRetries | 10 | (integer) The number of reconnection attempts before giving up. |
| autoReconnect | true | (boolean) If false, library will not attempt reconnecting. |
| cf.enable | false | (boolean) Enable exposing client function for this connection. (Check Client Function section for details.) |

Connection

Once the properties are set, use connect() function to connect to dataBridges Network.

`javascript
dbridge.connect().catch((err) => {
console.log('dBridges Connection exception..', err.source, err.code, err.message);
});
`

#### Exceptions:

| Source | Code | Message | Description |
| ------------- | ---------------------- | ------------------------------- | ------------------------------------------------------------ |
| DBLIB_CONNECT | INVALID_URL | | Value of dbridge.auth_url is not a valid dataBridges authentication URL. |
| DBLIB_CONNECT | INVALID_AUTH_PARAM | | Value of dbridge.appkey or dbridge.appsecret is not a valid dataBridges application key. |
| DBLIB_CONNECT | ACCESSTOKEN_FAILED | | dbridge.appsecret validation failed. |
| DBLIB_CONNECT | HTTP_ | HTTP protocol reported message. | HTTP Errors returned during authentication process. HTTP Error code will be concatenated with HTTP_ in the err.code. eg. HTTP_501 |
| DBLIB_CONNECT | INVALID_CLIENTFUNCTION | | If "callback function" is not declared for client function or typeof() variable defined is not a "function". This is applicable only if clientFunction is enabled. (Check Client Function section for details.) |

#### sessionid (string)

`javascript
console.log(dbridge.sessionid);
`

Making a connection provides the application with a new sessionid that is assigned by the application. This can be used to distinguish the application's own events. A change of state might otherwise be duplicated in the application. It is also stored within the connection, and used as a token for generating signatures for private/presence/system channels/rpc functions.

#### disconnect (function)

To close a connection use disconnect function. When a connection has been closed explicitly, no automatic reconnection will happen.

`javascript
dbridge.disconnect();
`

Objects

| Object | Description |
| ----------------- | ------------------------------------------------------------ |
| connectionstate | connectionstate object expose properties, functions and events to monitor and manage the health of dataBridges network connection. |
| channel | channel object exposes trust-safe flexible Pub/Sub messaging properties, functions and events to build realtime event messaging / event driven applications at scale. |
| rpc | rpc object exposes trust-safe properties, functions and events to provide reliable two-way messaging between multiple endpoints allowing you to build sophisticated asynchronous interactions. |
| cf | CF (Client-function) object is a special purpose RPC implementation to build command and control applications. CF object exposes properties, functions and events for command and control applications to send messages to devices and application using dataBridges client library in trust-safe manner , build smart update configuration system and implement trust-safe actions for remote and automated management. |

object:ConnectionState

Connectionstate object expose properties, functions and events to monitor and manage the health of dataBridges network connection.

$3

The following is the list of connection state properties.

`javascript
console.log(dbridge.connectionstate.state);
console.log(dbridge.connectionstate.isconnected);
console.log(dbridge.connectionstate.rttms);
console.log(dbridge.connectionstate.reconnect_attempt);
`

| Property | Description |
| ----------------------------------- | ------------------------------------------------------------ |
| connectionstate.state | (String) Current state of dataBridges network connection . List of Return Values are detailed below. |
| connectionstate.isconnected | (Boolean) To verify if the application is still connected to the dataBridges network. |
| connectionstate.rttms | (integer) Latency in milliseconds between your application and the dataBridges router where your application is connected. |
| connectionstate.reconnect_attempt | (integer) Number of reconnection attempted as of now. |

##### connectionstate.state

| Return Values | Description |
| ------------------ | ------------------------------------------------------------ |
| connecting | Your application is now attempting to connect to dataBridges network. |
| connected | The connection to dataBridges network is open and authenticated with your appkey. |
| connection_break | Indicates a network disconnection between application and dataBridges network. The library will initiate an automatic reconnection, if the reconnection property is set as true. |
| connect_error | This event will show system messages related to dataBridges network as well as Rate-limit exceptions (details in Rate-limit section). |
| disconnected | The application is now disconnected from the dataBridges network. The application will than need to initiate fresh connection attempt again. |
| reconnecting | Your application is now attempting to reconnect to dataBridges network as per properties set for reconnection. |
| reconnect_error | Reconnection attempt has errored. |
| reconnect_failed | The application will enter reconnect_failed state when all the reconnection attempts have been exhausted unsuccessfully. The application is now disconnected from the dataBridges network. The application will than need to initiate fresh connection attempt again |
| reconnected | The application has successfully re-connected to the dataBridges network, This state will follow connect_error or reconnect_error. |

$3

Apart from retrieveing state of a dBrige connection, application can bind to connectionstate events.

You can use the following methods on connectionstate object to bind to events.

`javascript
dbridge.connectionstate.bind(eventName, () => {});
dbridge.connectionstate.unbind(eventName);
dbridge.connectionstate.unbind();
`

bind() on eventName has callback functions to be defined where you can write your own code as per requirement.

To stop listening to events use unbind(eventName) function.

To stop listening to all events use unbind() [without eventName] function.

Below are library events which can be bind to receive information about dataBridges network.

#### System events for connectionstate object

`js
dbridge.connectionstate.bind("connecting", () => {
console.log('connecting');
});
dbridge.connectionstate.bind("reconnecting", () => {
console.log('reconnecting', "reconnect_attempt=", dbridge.connectionstate.reconnect_attempt);
});
dbridge.connectionstate.bind("disconnected", () => {
console.log('disconnected');
});
dbridge.connectionstate.bind("reconnected", () => {
console.log('reconnected');
});
dbridge.connectionstate.bind("connection_break", (payload) => {
console.log('connection_break', payload.source, payload.code, payload.message);
});
dbridge.connectionstate.bind("state_change", (payload) => {
console.log('state_change', dbridge.connectionstate.state, payload);
});
dbridge.connectionstate.bind("connect_error", (payload) => {
console.log('connect_error', payload.source, payload.code, payload.message);
});
dbridge.connectionstate.bind("reconnect_error", (payload) => {
console.log('reconnect_error', payload.source, payload.code, payload.message);
});
dbridge.connectionstate.bind("reconnect_failed", (payload) => {
console.log('reconnect_failed', payload.source, payload.code, payload.message);
});
dbridge.connectionstate.bind("rttpong", (payload) => {
console.log('rttpong', payload, dbridge.connectionstate.rttms);
});
dbridge.connectionstate.bind("connected", () => {
console.log('connected');
});
`
###### payload: (dberror object)

`javascript
{
"source": "DBLIB_CONNECT" , // (string) Error source
"code": "RECONNECT_ATTEMPT_EXCEEDED", // (string) Error code
"message": "" // (string) Error message if applicable.
}
`

| Events | Parameters | Description |
| ------------------ | -------------------------------------------------- | ------------------------------------------------------------ |
| connecting | | This event is triggered when your application is attempting to connect to dataBridges network. |
| connected | | This event is triggered when connection to dataBridges network is open and authenticated with your appkey. |
| connection_break | payload | (dberror object) Indicates a network disconnection between application and dataBridges network. The library will initiate an automatic reconnection, if the reconnection property is set as true. |
| connect_error | payload | (dberror object) This event is triggered when the dataBridges network connection was previously connected and has now errored and closed. |
| disconnected | | The application is now disconnected from the dataBridges network. The application will than need to initiate fresh connection attempt again. |
| reconnecting | | This event is triggered when application is now attempting to reconnect to dataBridges network as per properties set for reconnection. |
| reconnect_error | payload | (dberror object) This event is triggered when reconnection attempt has errored. |
| reconnect_failed | payload | (dberror object) reconnect_failed event is triggered when all the reconnection attempts have been exhaused unsuccessfully. The application is now disconnected from the dataBridges network. The application will than need to initiate fresh connection attempt again. |
| reconnected | | This event is triggered when the connection to dataBridges network is open and reconnected after connect_error or reconnect_error. |
| state_change | payload with payload.previous, payload.current | (dict) This event is triggered whenever there is any state changes in dataBridges network connection. Payload will have previous and current state of connection. |
| rttpong | payload | (integer) In Response to rttping() function call to dataBridges network, payload has latency in milliseconds between your application and the dataBridges router where your application is connected. |

#### dberror:

| Source | Code | Message | Description |
| ------------- | -------------------------- | ------------------------------- | ------------------------------------------------------------ |
| DBLIB_CONNECT | RECONNECT_ATTEMPT_EXCEEDED | | Triggered when reconnect_failed event is raised. |
| DBNET_CONNECT | DISCONNECT_REQUEST | | Triggered when connect_error event is raised. |
| DBNET_CONNECT | RECONNECT_REQUEST | | Triggered when connect_error, connection_break event is raised. |
| DBLIB_CONNECT | NETWORK_DISCONNECTED | | Triggered when connect_error, reconnect_error event is raised. |
| DBLIB_CONNECT | INVALID_URL | | Value of dbridge.auth_url is not a valid dataBridges authentication URL. |
| DBLIB_CONNECT | INVALID_AUTH_PARAM | | Value of dbridge.appkey or dbridge.appsecret is not a valid dataBridges application key. |
| DBLIB_CONNECT | ACCESSTOKEN_FAILED | | dbridge.appsecret validation failed. |
| DBLIB_CONNECT | HTTP_ | HTTP protocol reported message. | HTTP Errors returned during authentication process. HTTP Error code will be concatenated with HTTP_ in the err.code. eg. HTTP_501 |
| DBLIB_CONNECT | INVALID_CLIENTFUNCTION | | If "callback function" is not declared for client function or typeof() variable defined is not a "function". (Check Client Function section for details.) |

#### Exceptions:

| Source | Code | Description |
| ------------------ | ----------------- | ------------------------------------------------------------ |
| DBLIB_CONNECT_BIND | INVALID_EVENTNAME | Invalid Event name. Not in defined events as above. |
| DBLIB_CONNECT_BIND | INVALID_CALLBACK | If "callback function" is not declared or typeof() variable defined is not a "function". |

$3

#### rttping()

This method is to understand the latency in milliseconds between your application and the dataBridges router where your application is connected. Event rttpong is triggered once response is received from dataBridges network. Bind to event:rttpong to retrieve the latency in ms.

`js
// To get the last known Latency in milliseconds between your application and the dataBridges router where your application is connected.
// The dataBridges library exchanges rttms during the initial dataBridges network connection routine.
console.log(dbridge.connectionstate.rttms);

// To get the latest Latency in milliseconds between your application and the dataBridges router where your application is connected.
dbridge.connectionstate.rttping();

// Bind to rttpong, to get notified about the latest Latency in milliseconds between your application and the dataBridges router where your application is connected.
dbridge.connectionstate.bind("rttpong", (payload) => {
console.log('rttpong', payload);
//payload is an integer value is in millisecond which is same as dbridge.connectionstate.rttms.
});
`

#### Exceptions:

| Source | Code | Description |
| ------------- | -------------------- | ------------------------------------------------ |
| DBLIB_RTTPING | NETWORK_DISCONNECTED | Connection to dataBridges network is not active. |

------

object:Channel

channel object exposes trust-safe flexible Pub/Sub messaging properties, functions and events to build realtime event messaging / event driven applications at scale.

Concepts

- A message is attached to an event
- Group similar events into a channel
- Subscribe to a channel to receive all channel event messages.
- Publish event message to the channel and it will be sent to all the channel subscribers who are connected to dataBridges network and online.
- if you need to have an access controlled channel, prefix the channel name with pvt: , prs: and sys: .
- Note dataBridges have 2 seprate libraries (client lib, server lib). You are reading the server library api document.
- Server lib uses app.key along with secret to get access to all channels including pvt: , prs: and sys: channels linked to the application.
- Whereas application using client library (client application) will always need to pass a trust-token to access restricted channels (pvt: prs: sys: ) . A trust-token is a JWT document created using a combination of channelname + sessionid + app.secret. Trust token can be created by application having access to app.key's secret.
- you can use your existing access control, authorization and session identification rule-set, process and methods to create a trust-token instructing the dataBridges router to accept the pvt: prs: and sys: channel subscription, connection of from client application.
- Trust-tokens allows you to enable secured, access controlled and compliance driven realtime event driven messaging in your existing and new initiative applications.


dataBridges library supports 4 types of channel. The namespace is the 4 characters preceding the channelName (pvt:,prs:,sys:), identifying which type of channel the application is connecting to.

| Channel Type | Channel Name Style | Description |
| ------------ | ------------------ | ------------------------------------------------------------ |
| Public | channelName | Public channel is used to send and receive messages that are to be publicly available. This channel type does not require any trust authorization token to subscribe.
e.g channelName = mychannel |
| Private | pvt:channeName | Private channels is restricted channel. e.g channelName = pvt:mychannel |
| Presence | prs:channeName | Presence channels is a specialized private channel with additional feature of presence awareness. Subscribing to presence channel allows application to be notified of members joining / leaving the channel. e.g channelName = prs:mychannel |
| System | sys:channeName | System channel is a specialized Presence channel to build command and control applications. Using System channel to create command and control server applications to send messages to devices and application using dataBridges library in trust-safe manner , build smart update configuration system and implement trust-safe actions for remote and automated management. System channel allows application to send and receive messages with the server application (using dataBridges server library).
e.g channelName = sys:systeminfo |

$3

Application that subscribes to a channel will receive messages and can send messages.

#### subscribe()

The default method for subscribing to a channel involves invoking the channel.subscribe function of your dataBridges object:

`js
try {
const subscribed_channel = dbridge.channel.subscribe('mychannel');
} catch (err) {
console.log(err.source, err.code, err.message);
}
`

| Parameter | Rules | Description |
| --------- | ------------------------------------------------------------ | ----------------------------------------------- |
| string | channelName OR
pvt:channelName OR
prs:channelName OR
sys:channelNameOR
sys: | channelName* to which subscription to be done. |

| Return Type | Description |
| ----------- | ------------------------------------------------------------ |
| object | channel object which events and related functions can be bound to. |

Application can directly work with dataBridges object without using Channel object.

`js
try {
dbridge.channel.subscribe('mychannel');
} catch (err) {
console.log(err.source, err.code, err.message);
}
`

##### Exceptions:

| Source | Code | Description |
| ----------------------- | -------------------------- | ------------------------------------------------------------ |
| DBLIB_CHANNEL_SUBSCRIBE | NETWORK_DISCONNECTED | Connection to dataBridges network is not active. |
| DBLIB_CHANNEL_SUBSCRIBE | INVALID_CHANNELNAME | Applicable for below conditions
1. channelName is not defined.
2. channelName validation error, typeof() channelName is not type string
3. channelName validation error, channelName fails a-zA-Z0-9\.:_- validation. |
| DBLIB_CHANNEL_SUBSCRIBE | INVALID_CHANNELNAME_LENGTH | channelName validation error, length of channelName greater than 64 |
| DBLIB_CHANNEL_SUBSCRIBE | CHANNEL_ALREADY_SUBSCRIBED | channelName is already subscribed. |

#### unsubscribe()

To unsubscribe from a subscribed channel, invoke the unsubscribe function of your dataBridges object. unsubscribe cannot be done on channel object.

`javascript
try {
dbridge.channel.unsubscribe('mychannel');
} catch (err) {
console.log(err.source, err.code, err.message);
}
`

| Parameter | Rules | Description |
| --------- | ------------------------------------------------------------ | -------------------------------------------------- |
| string | channelName OR
pvt:channelName OR
prs:channelName OR
sys:channelName | channelName to which un-subscription to be done. |

| Return Type | Description |
| ----------- | ----------- |
| NA | |

##### Exceptions:

| Source | Code | Description |
| ------------------------- | ----------------------------- | ------------------------------------------------------------ |
| DBLIB_CHANNEL_UNSUBSCRIBE | NETWORK_DISCONNECTED | Connection to dataBridges network is not active. |
| DBLIB_CHANNEL_UNSUBSCRIBE | CHANNEL_NOT_SUBSCRIBED | channelName is not subscribed. |
| DBLIB_CHANNEL_UNSUBSCRIBE | UNSUBSCRIBE_ALREADY_INITIATED | unsubscription to the channel is already initiated and hence the current unsubscribe command exited with exception. |

$3

#### isOnline()

dBridgeObject as well as channelObject provides a function to check if the channel is online. The best practice is to check the channel is online before publishing any message.

`js
const mychannel_isonline = dbridge.channel.isOnline('mychannel');
`

`js
const mychannel_isonline = subscribed_channel.isOnline();
`

| Parameter | Rules | Description |
| --------- | ------------------------------------------------------------ | ------------- |
| string | channelName OR
pvt:channelName OR
prs:channelName OR
sys:channelName | channelName |

| Return Values | Description |
| ------------- | --------------------------------------------------- |
| boolean | Is the current status of channel online or offline. |

#### list()

dBridgeObject provides a function to get list of successfully subscribed or connected channel.

`javascript
const channels = dbridge.channel.list();
#=> [{"name": "mychannel" , "type": "subscribed/connect" , "isonline": true/false }];
`

| Return Type | Description |
| --------------- | ------------------------------------------ |
| array of dict | Array of channels subscribed or connected. |

Dictionary contains below information.

| Key | Description |
| ---------- | ------------------------------------------------------------ |
| name | (string) channelName of subscribed or connected channel. |
| type | (string) subscribed |
| isonline | (boolean) Is the current status of channel online or offline. |

#### getChannelName()

channelObject provides a function to get the channelName.

`js
const chName = channelobject.getChannelName()
`

| Return Type | Description |
| ----------- | ------------------------------------ |
| string | channelName of subscribed channel. |

$3

Publish event-message using the publish function on an instance of the channel object.

A message is linked to an event and hence event-message. dataBridges allows you to bind to various events to create rich event processing flows.

#### publish()

The default method for publishing user-defined events to a channel involves invoking the channel.publish function of your channelObject for which it has connected to OR using dbridgeObject giving the channelName as parameter.

Note: channel.publish is not allowed using channelObject subscribed to sys:* channel.

`javascript
// Using dbridgeObject
try {
dbridge.channel.publish(channelName, event, payload, excludeSessionId, sourceId, seqno);
} catch (err) {
console.log(err.source, err.code, err.message);
}
// Using channelObject
try {
channelObject.publish(event, payload, excludeSessionId, sourceId, seqno);
} catch (err) {
console.log(err.source, err.code, err.message);
}
// Best practice is to check the channel is online before publishing any message.
if (channelObject.isOnline()) {
try {
channelObject.publish(event, payload, excludeSessionId, sourceId, seqno);
} catch (err) {
console.log(err.source, err.code, err.message);
}
}
`

| Parameter | Description |
| ------------------ | ------------------------------------------------------------ |
| channelName | (string) Channel name for which details are required. |
| event | (string) event Name to which the message to be sent. event Name cannot start with dbridges: |
| payload | (string) Payload to be sent with the event. |
| excludeSessionId | (string) Excludes the event from being sent to a specific sessionid (connection).

For example when a server application (example: chat server) sends event message on behalf of a specific session ( example: chat user) to a channel (example: chat group), the sessionID (example: chat user) will be excluded to receive its own message. |
| sourceId | (string) Required in case of presence(prs:) and system (sys:) channel. When sending a message to a presence(prs:) or system (sys:) channel, application need to specify a message source by using this sourceId.

For example when a server application (example: chat server) sends event message on behalf of a specific session ( example: chat user) to a channel (example: chat group), the sourceID (example: chat user information) can be attached usiing sourceID to the event message. This allows all message receipient to know who has sent the message. |
| seqno | (string) [optional] Message sequence number. This is optional parameter. seqno can be used by applications to manage message queue processing by the subscribers. |

| Return Values | Description |
| ------------- | ----------- |
| NA | |

##### Exceptions:

| Source | Code | Description |
| --------------------- | -------------------------- | ------------------------------------------------------------ |
| DBLIB_CHANNEL_PUBLISH | NETWORK_DISCONNECTED | Connection to dataBridges network is not active. |
| DBLIB_CHANNEL_PUBLISH | INVALID_CHANNELNAME | Applicable for below conditions
1. channelName validation error, typeof() channelName is not type string
2. channelName validation error, channelName fails a-zA-Z0-9\.:_- validation.
3. channelName is sys:
4. channelName* is not defined. |
| DBLIB_CHANNEL_PUBLISH | INVALID_CHANNELNAME_LENGTH | channelName validation error, length of channelName greater than 64 |
| DBLIB_CHANNEL_PUBLISH | INVALID_SUBJECT | Applicable for below conditions
1. event validation error, event is not defined
2. event validation error, typeof() event is not type string |

$3

It's possible to send message to individual sessionId using the channel.sendmsg function on an instance of the channelObject or using dbridgeObject.

#### sendmsg()

The default method for send message user-defined events to a individual sessionId involves invoking the channel.sendmsg function of your channelObject for which it has connected to OR using dbridgeObject giving the channelName as parameter.

Note: channel.sendmsg is not allowed using channelObject subscribed to sys:* channel.

`javascript
// Using dbridgeObject
try {
dbridge.channel.sendmsg(channelName, event, payload, toSessionId, sourceId, seqno);
} catch (err) {
console.log(err.source, err.code, err.message);
}
// Using channelObject
try {
channelObject.sendmsg(event, payload, toSessionId, sourceId, seqno);
} catch (err) {
console.log(err.source, err.code, err.message);
}

// Best practice is to check the channel is online before publishing any message.
if (channelObject.isOnline()) {
try {
channelObject.sendmsg(event, payload, toSessionId, sourceId, seqno);
} catch (err) {
console.log(err.source, err.code, err.message);
}
}
`

| Parameter | Description |
| ------------- | ------------------------------------------------------------ |
| channelName | (string) Channel name for which details are required. |
| event | (string) event Name to which the message to be sent. event Name cannot start with dbridges: |
| payload | (string) Payload to be sent with the event. |
| toSessionId | (string) sessionid where the message to be sent. |
| sourceId | (string) Required in case of presence(prs:) and system (sys:) channel. When sending a message to a presence(prs:) or system (sys:) channel, application need to specify a message source by using this sourceId.

For example when a server application (example: chat server) sends event message on behalf of a specific session ( example: chat user) to a channel (example: chat group), the sourceID (example: chat user information) can be attached usiing sourceID to the event message. This allows all message receipient to know who has sent the message. |
| seqno | (string) [optional] Message sequence number. This is optional parameter. seqno can be used by applications to manage message queue processing by the subscribers. |

| Return Values | Description |
| ------------- | ----------- |
| NA | |

##### Exceptions:

| Source | Code | Description |
| --------------------- | -------------------------- | ------------------------------------------------------------ |
| DBLIB_CHANNEL_SENDMSG | NETWORK_DISCONNECTED | Connection to dataBridges network is not active. |
| DBLIB_CHANNEL_SENDMSG | INVALID_CHANNELNAME | Applicable for below conditions
1. channelName validation error, typeof() channelName is not type string
2. channelName validation error, channelName fails a-zA-Z0-9\.:_- validation.
3. channelName is sys:
4. channelName is not defined.
5. channelType is prs: and sourceId is not provided.
6. channelName* contains : and first token is not pvt,prs,sys |
| DBLIB_CHANNEL_SENDMSG | INVALID_CHANNELNAME_LENGTH | channelName validation error, length of channelName greater than 64 |

$3

A message is linked to an event and hence event-message. dataBridges allows you to bind to various events to create rich event processing flows. An application needs to bind to event to process the received message.

You can use the following methods either on a channelObject, to bind to events on a particular channel; or on the dbridgeObject, to bind to events on all subscribed channels simultaneously.

#### bind and unbind

Bind to "event" on channel: payload and metadata is received.

`javascript
// Binding to channel events on channelObject using Anonymous function.
try {
channelObject.bind('eventName', (payload, metadata) => {
console.log(payload, metadata);
});
} catch(err){
console.log(err.source, err.code, err.message);
}

// Binding to channel events on dbridgeObject using Anonymous function.
try {
dbridge.channel.bind('eventName', (payload, metadata) => {
console.log(payload, metadata);
});
} catch(err){
console.log(err.source, err.code, err.message);
}

// Binding to channel events on channelObject using user function.
const myEventHandler = (payload, metadata) =>{
console.log(payload, metadata);
};

try {
dbridge.channel.bind('eventName', myEventHandler);
} catch(err){
console.log(err.source, err.code, err.message);
}
`

| Parameter | Description |
| --------- | ---------------------------------------------------- |
| event | (string) event Name to which binding to be done. |

##### Callback parameters

###### payload:

(string) Payload data sent by the publisher.

###### metadata (dict):

`json
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "event", // (string) eventName
"sourcesysid": "", // (string) Sender system identity, applicable only for presence or system channel.
"sqnum": "1", // (string) user defined, sent during publish function.
"sessionid": "", // (string) Sender sessionid, applicable only for presence or system channel.
"intime": 25 // (int) Intime is a metric that quantifies the routing latency within the messaging infrastructure, specifically within the context of the messaging platform. It measures the time it takes for an event message to traverse from the moment it is received by the messaging to the instant it is dispatched to the subscriber(s) of the event. InTime is expressed in milliseconds (ms) and serves as a crucial indicator of the efficiency and responsiveness of the messaging system. This metric Not applicable for system events.
}
`

##### Exceptions:

| Source | Code | Description |
| ------------------ | ----------------- | ------------------------------------------------------------ |
| DBLIB_CONNECT_BIND | INVALID_EVENTNAME | Invalid Event name. Not in user-defined events or default events. |
| DBLIB_CONNECT_BIND | INVALID_CALLBACK | If "callback function" is not declared or typeof() variable defined is not a "function". |

Unbind behavior varies depending on which parameters you provide it with. For example:

`js
// Remove just handler of the event in the subscribed/connected channel
channelObject.unbind('eventName',handler);

// Remove all handler of the event in the subscribed/connected channel
channelObject.unbind('eventName');

//Remove all handlers for the all event in the subscribed/connected channel
channelObject.unbind();

// Remove handler of the event for all events across all subscribed/connected channels
dbridge.channel.unbind('eventName',handler);

// Remove all handlers of the event for all events across all subscribed/connected channels
dbridge.channel.unbind('eventName');

// Remove all handlers for all events across all subscribed/connected channels
dbridge.channel.unbind();
`

#### bind_all and unbind_all

bind_all and unbind_all work much like bind and unbind, but instead of only firing callbacks on a specific event, they fire callbacks on any event, and provide that event in the metadata to the handler along with the payload.

`js
// Binding to all channel events on channelObject
try {
channelObject.bind_all((payload, metadata) => {
console.log(payload, metadata);
});
} catch(err){
console.log(err.source, err.code, err.message);
}

// Binding to all channel events on dbridgeObject
try {
dbridge.channel.bind_all((payload, metadata) => {
console.log(payload, metadata);
});
} catch(err){
console.log(err.source, err.code, err.message);
}
`

Callback out parameter payload, metadata details are explained with each event below in this document.

##### Exceptions:

| Source | Code | Description |
| ------------------ | ---------------- | ------------------------------------------------------------ |
| DBLIB_CONNECT_BIND | INVALID_CALLBACK | If "callback function" is not declared or typeof() variable defined is not a "function". |

unbind_all works similarly to unbind.

`js
// Remove just handler across the channel
channelObject.unbind_all(handler);

//Remove all handlers for the all event in the subscribed/connected channel
channelObject.unbind_all();

// Remove handler across the subscribed/connected channels
dbridge.channel.unbind_all(handler);

// Remove all handlers for all events across all subscribed/connected channels
dbridge.channel.unbind_all();
`

$3

There are a number of events which are triggered internally by the library, but can also be of use elsewhere. Below are the list of all events triggered by the library.

Below syntax is same for all system events.

`javascript
// Binding to systemevent on channelObject
try {
channelObject.bind('dbridges:subscribe.success', (payload, metadata) => {
console.log( payload, metadata);
});
} catch(err) {
console.log(err.source, err.code, err.message);
}
// Binding to systemevent on dbridgeObject
try {
dbridge.channel.bind('dbridges:subscribe.success', (payload, metadata) => {
console.log( payload, metadata);
});
} catch(err) {
console.log(err.source, err.code, err.message);
}
`

##### dbridges:subscribe.success

###### Callback parameters

payload:

null

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:subscribe.success",// (string) eventName
"sourcesysid": "", // (string) Sender system identity, applicable only for presence or system channel.
"sqnum": "1", // (string) user defined, sent during publish function.
"sessionid": "", // (string) Sender sessionid, applicable only for presence or system channel.
"intime": null
}
`

##### dbridges:subscribe.fail

###### Callback parameters

payload: (dberror object)

`javascript
{
"source": "dberror.Source" , // (string) Error source, Refer dberror: for details
"code": "dberror.Code", // (string) Error code, Refer dberror: for details
"message": "" // (string) Error message if applicable.
}
`

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:subscribe.fail",// (string) eventName
"sourcesysid": "", // (string)
"sqnum": "", // (string)
"sessionid": "", // (string)
"intime": null
}
`

##### dbridges:channel.online

###### Callback parameters

payload:

null

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:channel.online",// (string) eventName
"sourcesysid": "", // (string)
"sqnum": "", // (string)
"sessionid": "", // (string)
"intime": null
}
`

##### dbridges:channel.offline

###### Callback parameters

payload:

null

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:channel.offline",// (string) eventName
"sourcesysid": "", // (string)
"sqnum": "", // (string)
"sessionid": "", // (string)
"intime": null
}
`

##### dbridges:channel.removed

###### Callback parameters

payload:

null

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:channel.removed",// (string) eventName
"sourcesysid": "", // (string)
"sqnum": "", // (string)
"sessionid": "", // (string)
"intime": null
}
`

##### dbridges:unsubscribe.success

###### Callback parameters

payload:

null

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:unsubscribe.success",// (string) eventName
"sourcesysid": "", // (string)
"sqnum": "", // (string)
"sessionid": "", // (string)
"intime": null
}
`

##### dbridges:unsubscribe.fail

###### Callback parameters

payload: (dberror object)

`javascript
{
"source": "dberror.Source" , // (string) Error source, Refer dberror: for details
"code": "dberror.Code", // (string) Error code, Refer dberror: for details
"message": "" // (string) Error message if applicable.
}
`

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:unsubscribe.fail",// (string) eventName
"sourcesysid": "", // (string)
"sqnum": "", // (string)
"sessionid": "", // (string)
"intime": null
}
`

##### dbridges:resubscribe.success

###### Callback parameters

payload:

null

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:resubscribe.success",// (string) eventName
"sourcesysid": "", // (string)
"sqnum": "", // (string)
"sessionid": "", // (string)
"intime": null
}
`

##### dbridges:resubscribe.fail

###### Callback parameters

payload: (dberror object)

`javascript
{
"source": "dberror.Source" , // (string) Error source, Refer dberror: for details
"code": "dberror.Code", // (string) Error code, Refer dberror: for details
"message": "" // (string) Error message if applicable.
}
`

metadata (dict):

`javascript
{
"channelname": "channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:resubscribe.fail",// (string) eventName
"sourcesysid": "", // (string)
"sqnum": "", // (string)
"sessionid": "", // (string)
"intime": null
}
`

##### dbridges:participant.joined

This will be triggered only for presence (prs:) and system (sys:) channel subscription.

###### Callback parameters

payload: (dict)

`javascript
{
"sessionid": "ydR27s3Z92yQw7wjGY2lX", // (string) Session id of the member who has subscribed/connected to channel
"libtype": "nodejs", // (string) Library Lang of the member who has subscribed/connected to channel
"sourceipv4": "0.0.0.0", // (string) IPv4 of the member who has subscribed/connected to channel
"sourceipv6": "::1", // (string) Not Applicable in this version
"sysinfo": '{"sysid":"nameofcaller"}' // (string) System Info of the member who has subscribed/connected to channel
}
`

metadata (dict):

`javascript
{
"channelname": "prs:channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:participant.joined",// (string) eventName
"sourcesysid": "nameofcaller", // (string) Sys id of the member who has subscribed/connected to channel
"sqnum": null, // (string)
"sessionid": "ydR27s3Z92yQw7wjGY2lX", // (string) Session id of the member who has subscribed/connected to channel
"intime": null
}
`

##### dbridges:participant.left

This will be triggered only for presence (prs:) and system (sys:) channel subscription.

###### Callback parameters

payload: (dict)

`javascript
{
"sessionid": "ydR27s3Z92yQw7wjGY2lX", // (string) Session id of the member who has subscribed/connected to channel
"libtype": "nodejs", // (string) Library Lang of the member who has subscribed/connected to channel
"sourceipv4": "0.0.0.0", // (string) IPv4 of the member who has subscribed/connected to channel
"sourceipv6": "::1", // (string) Not Applicable in this version
"sysinfo": '{"sysid":"nameofcaller"}' // (string) System Info of the member who has subscribed/connected to channel
}
`

metadata (dict):

`javascript
{
"channelname": "prs:channelName" , // (string) channelName to which subscription is done.
"eventname": "dbridges:participant.left",// (string) eventName
"sourcesysid": "nameofcaller", // (string) Sys id of the member who has subscribed/connected to channel
"sqnum": null, // (string)
"sessionid": "ydR27s3Z92yQw7wjGY2lX", // (string) Session id of the member who has subscribed/connected to channel
"intime": null
}
`

##### System events - payload (dberror object) - details:

| Source | Code | Description |
| ------------------------- | ----------------- | ------------------------------------------------------------ |
| DBNET_CHANNEL_SUBSCRIBE | ERR_FAIL_ERROR | dataBridges network encountered error when subscribing to the channel. |
| DBNET_CHANNEL_SUBSCRIBE | ERR_ACCESS_DENIED | dBrdige network reported access violation with access_token function during subscription of this channel. |
| DBNET_CHANNEL_UNSUBSCRIBE | ERR_FAIL_ERROR | dataBridges network encountered error when unsubscribing to the channel. |
| DBNET_CHANNEL_UNSUBSCRIBE | ERR_ACCESS_DENIED | dataBridges network reported access violation with access_token function during unsubscribing of this channel. |

------

object: rpc (Remote Procedure Call)

rpc object exposes trust-safe properties, functions and events to provide reliable two-way messaging (request-response) between multiple endpoints allowing you to build sophisticated asynchronous interactions.

Concepts

- RPC endpoint / server (CALLEE)
- Application using dataBridges server library can expose callback function(s) as a dataBridges rpc function.
- Multiple callback function(s), can be exposed as rpc functions grouped together as an rpc endpoint / server.
- To deploy access-controlled, trust-safe rpc endpoint / server, prefix the rpc server namespace with pvt: or prs:
- Note dataBridges have 2 seprate libraries (client lib, server lib). You are reading the server library api document.
- Server lib uses app.key along with secret to get access to rpc endpoint/server including pvt: , prs: access controlled rpc endpoint/server.
- Whereas application using client library (client application) will always need to pass a trust-token to access restricted rpc endpoint/server (prefixed with pvt: prs:) . A trust-token is a JWT document created using a combination of channelname + sessionid + app.secret. Trust token can be created by application having access to app.key's secret.
- you can use your existing access control, authorization and session identification rule-set, process and methods to create a trust-token instructing the dataBridges router to accept the pvt: prs: rpc call() client application.
- Trust-tokens allows you to enable secured, access controlled and compliance driven two-way messaging (request-response) between multiple endpoints allowing you to build sophisticated asynchronous interactions in your existing and new initiative applications.
- RPC clients (CALLER)
- Both dataBridges client and server api's allow you to execute rpc function(s) exposed by rpc endpoint / server.
- Appication consuming rpc function(s) is called CALLEE and the rpc endpoint/server application is called CALLER.
- CALLEE application will execute a remote function by passing IN.paramter, and a timeout
- The CALLER application's corresponding function will be invoked with the IN.parameter and it will respond with response() or exception() which will be delivered back to the CALLEE application by dataBridges network completing the request-response communication.
- CALLEE application need not be aware about RPC servers (CALLER) identity and will only interact with RPC server (CALLER) namespace. The dataBridges network will intelligently route and load balance RPC call() to the RPC server application. The dataBridges network will automatically load balance multiple instance of server application exposing the same RPC endpoints.

To expose rpc functions the application needs to register an rpc server and register callback functions to rpc server as rpc functions.

- The steps involved are :
- Initialize rpc endpoint/server using init().
- Register all rpc functions using regfn().
- Register rpc endpoint/server with dataBridges network using register()

$3

Initialize the server using rpc.init function of your dataBridges object. This will return an object to which all properties, functions and events are available.

Note : Application can have multiple rpc endpoint/server against a dataBridges object.

`js
//lets create an rpc endpoint/server named missionControl and expose 2 functions called nasa and isro.

try {
const missionControl = dbridge.rpc.init('missionControl');
} catch (err) {
console.log(err.source, err.code, err.message);
}
`

| Parameter | Rules | Description |
| --------- | ------------------------------------------------------------ | -------------------------------------------- |
| string | serverName OR
pvt:serverName OR
prs:serverName | Initialize a rpcServer with serverName . |

| Return Type | Description |
| ----------- | ------------------------------------------------------------ |
| object | rpcObject which events, properties and related functions can be bound to. |

##### Exceptions:

| Source | Code | Description |
| -------------- | ------------------ | ------------------------------------------------------------ |
| DBLIB_RPC_INIT | INVALID_SERVERNAME | Applicable for below conditions
1. serverName is not defined.
2. serverName already exists
3. serverName is blank.
4. serverName validation error, length of serverName greater than 64
5. serverName validation error, serverName fails a-zA-Z0-9\.:_- validation.
6. serverName contains : and first token is not pvt,prs. |

$3

Application can expose callback function(s) as rpc functions. Application using dataBridges client/server library can remotely execute the rpc functions. Each function needs to be registered with the library as a rpc function, using rpc.regfn()where you can link the functionName to rpcFunctionName.

- The server application that exposes the rpc function is called a CALLEE.
- The client/server application that executes the rpc function is called a CALLER.

Functions can be defined either inside the property callback function or anywhere in the scope of application. Below code exhibits both ways of exposing the function.

`javascript
// function is exposed outside the property callback function, but in the scope of application.
function rpcFuncOustide (payload, response) {
try {
response.tracker = true;
response.next('This is Houston');
response.end('message received by Houston');
response.exception('INVALID_PARAM', 'Wrong parameter');
} catch(err) {
console.log(err.source, err.code, err.message);
}
}

missionControl.functions = function () {
// function is exposed inside the property callback function.
function rpcFuncInside (payload, response) {
try {
response.tracker = true;
response.next('This is Hassan');
response.end('message received by Hassan');
response.exception('INVALID_PARAM', 'Wrong parameter');
console.log(response.id);
} catch(err) {
console.log(err.source, err.code, err.message);
}
}
// registering function to be exposed by rpcServer
try {
missionControl.regfn("nasa", rpcFuncOustide);
missionControl.regfn("isro", rpcFuncInside);
} catch(err) {
console.log(err.source, err.code, err.message);
}
}

// unregistering of function exposed by rpcServer
missionControl.unregfn("nasa", rpcFuncOustide);
`

Below are parameters of the callback function which is exposed to rpcServer.

| Parameter | Description |
| ---------- | ------------------------------------------------------------ |
| payload | (object) Input payload from the caller. |
| response | (object) Response object having properties and function to return execution results of the function back to caller. |

##### payload: (object)

| Properties/Function | Description |
| ------------------- | ------------------------------------------------------------ |
| inparam | (string) Input parameters received to execute the function. |
| sessionid | (string) Session id of the member who has requested to execute the function. |
| libtype | (string) Library Lang of the member who has requested to execute the function. |
| sourceipv4 | (string) IPv4 of the member who has who has requested to execute the function. |
| sourceipv6 | (string) IPv6 of the member who has who has requested to execute the function. |
| info | (string) System Info of the member who has who has requested to execute the function. |

##### response: (object)

| Properties/Function | Description |
| ------------------- | ------------------------------------------------------------ |
| tracker | (boolean) This will enable response tracker, and event rpc.response.tracker will be fired if any issue happens in sending back response to caller. Enable this property if your function needs a confirmation of response delivered to the caller. |
| id | (string) (readonly) Each rpc function execution is assigned a unique ID by the library. when the response tracker is enabled, the application can bind to an event rpc.response.tracker to get the delivery notification. The event will indicate the delivery notification linked to this ID. Caller application will need to maintain this ID to track the delivery notification. |
| next | (function) dataBridges rpc supports mult-part response. Application can use response.next to send multi-part response to the caller. |
| end | (function) response.end is to send the final response to the caller. Once end is called, the object is closed and no more response can be sent. |
| exception | (function) Two parameter, return errorCode (string) ,errorMessage (string) is sent to caller. This will raise an exception at the caller library. |

##### Exceptions:

Below exceptions are raised in the rpc.regfn.

| Source | Code | Description |
| --------------- | --------------------- | --------------------------------------------- |
| DBLIB_RPC_REGFN | INVALID_FUNCTION_NAME | Invalid Function name. |
| DBLIB_RPC_REGFN | INVALID_CALLBACK | Callback is not a function or is not defined. |

Below exceptions are raised on response object inside the registered function.

| Source | Code | Description |
| -------------- | ---------------------- | ------------------------------------------------------------ |
| DBNET_RPC_CALL | NETWORK_DISCONNECTED | Connection to dataBridges network is not active. |
| DBLIB_RPC_CALL | RESPONSE_OBJECT_CLOSED | Return response object is closed. Thus the function is unable to respond back to the call. |

$3

Register rpc endpoint/server with dataBridges network using register().

`javascript
try {
missionControl.register();
} catch (err) {
console.log(err.source, err.code, err.message);
}

// Best practice is to check the channel is online before publishing any message.
if (dbridge.connectionstate.isconnected()) {
try {
missionControl.register();
} catch (err) {
console.log(err.source, err.code, err.message);
}
}
`

##### Exceptions:

| Source | Code | Description |
| ------------------ | --------------------- | ------------------------------------------------------------ |
| DBLIB_RPC_REGISTER | RPC_INVALID_FUNCTIONS | Applicable for below conditions
1. If "callback function" is not declared for rpc server
2. typeof() variable defined is not a "function". |
| DBLIB_RPC_REGISTER | NETWORK_DISCONNECTED | Connection to dataBridges network is not active. |

$3

rpcServer can be unregistered from dataBridges server library using unregister function of your rpcServerObject.

`javascript
missionControl.unregister();
`

$3

dbridgeObject The dataBridges network maintains in-process rpc function execution status. resetqueue() informs the dataBridges network that all in-process rpc function execution will be dropped by the application and response to be invalidated. Resetqueue() use case is intended to be used by application in its self health status management. Sometime due to the application process flow, the application can identify situation where it would like to ease its load by resettiing the rpc function execution queue by sending resetqueue() message to dataBridges network and than closing all in-process rpc function execution.

``javascript
try {
missionControl.resetqueue();
} catch(err) {
console.log(err.source, err.code, err.