databridges_sio_client_lib 2.0.5
Databridges Python client Library
Keywords: optomate, databridges, pubsub, rpc, websocket, socket.io, ws, events, realtime, real-time

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# Databridges Python client 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 Python client library allows you to easily add realtime capabilities to your applications in record time.

## Have you registered with dataBridges?

Registering allows you to access our production grade PlayGround network. You can take dataBridges for a spin and quickly create, test your proof of concepts without needing to create a payment account.

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](#supported-platforms)
- [Installation](#installation)
- [Initialization](#initialization)
- [Global Configuration](#global-configuration)
  - [Required](#required)
  - [Optional](#optional)
- [Connection](#connection)
- [Objects](#objects)
- [object:ConnectionState](#objectconnectionstate)
  - [Properties](#properties)
  - [Bind to connectionstate events](#bind-to-connectionstate-events)
  - [Functions](#functions)
- [object:Channel](#objectchannel)
  - [Subscribe to Channel](#subscribe-to-channel)
  - [Connect to Channel](#connect-to-channel)
  - [Channel Information](#channel-information)
  - [Publish to Channel](#publish-to-channel)
  - [Binding to events](#binding-to-events)
  - [System events for channel object](#system-events-for-channel-object)
- [object: rpc (Remote Procedure Call)](#object-rpc-remote-procedure-call)
  - [Connect to Server](#connect-to-server)
  - [Server Information](#server-information)
  - [Execute Remote Procedure Call](#execute-remote-procedure-call)
  - [System events for rpc object](#system-events-for-rpc-object)
- [object:Cf (Client Function)](#objectcf-client-function)
  - [Properties](#properties)
  - [System events for cf object](#system-events-for-cf-object)
- [Rate Limit and Concurrent connection](#rate-limit-and-concurrent-connection)
- [Change Log](#change-log)
- [License](#license)

## Supported platforms

Supports Python versions  +3.6

## Installation

You can use pip package manager to install the package.

```bash
pip3 install databridges_sio_client_lib
```

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

## Initialization

```python
from databridges_sio_client_lib import dBridges
from databridges_sio_client_lib.exceptions import dBError
dbridge = dBridges()
```

## Global Configuration

### Required

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

```python
dbridge.auth_url = 'URL'
dbridge.appkey = 'APP_KEY'
```

You need to replace `URL` and `APP_KEY` with the actual URL and Application Key.

| Properties | Description                                                  | Exceptions                                               |
| ---------- | ------------------------------------------------------------ | -------------------------------------------------------- |
| `auth_url` | *(string)* Authentication url from  [dataBridges dashboard](https://dashboard.databridges.io/). | `source: DBLIB_CONNECT` <br />`code: INVALID_URL`        |
| `appkey`   | *(string)* Application Key from  [dataBridges dashboard](https://dashboard.databridges.io/). | `source: DBLIB_CONNECT` <br />`code: INVALID_AUTH_PARAM` |

### Optional

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

```python
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 application 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, application will not attempt reconnecting. |
| `cf.enable`                   | `false`                       | *(boolean)* Enable exposing *client function* for this connection. (Check *Client Function* section for details.) |
| `access_token`                | `function`                    | *(function)* If you need custom authorization behavior for  generating signatures for private/ presence/ system channels/rpc functions, you can provide your own `access_token` function. |

## Connection

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

```python
try:
    await dbridge.connect()
except Exception as e:
	print("source: {0} ,  code: {1}, message: {2}".format(e.source , e.code , e.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` is not a valid dataBridges application key. |
| DBLIB_CONNECT | INVALID_ACCESSTOKEN_FUNCTION |                                 | If *"callback function"* is not declared for authentication **only** while using  **private, presence or system** channel/RPC functions. *(Check Channel or RPC section for details.)* |
| 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)*

```python
print("sessionid: {0}".format( dbridge.sessionid))
```

Making a connection provides the application with a new `sessionid` that is assigned by the server. 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.

```python
await 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 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. |



## object:ConnectionState

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

### Properties

The following is the list of connection state properties.

```python
print(dbridge.connectionstate.state)
print(dbridge.connectionstate.isconnected)
print(dbridge.connectionstate.rttms)
print(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`. |

### Bind to connectionstate events

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.

```python
dbridge.connectionstate.bind(eventName, callable)
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

```python
async def connecting():
    print("connecting")

async def reconnecting():
    print("reconnecting")

async def connection_break():
    print("connection_break")

async def state_change( data):
    print("state_change:", data)

async def connect_error( data):
    if isinstance(data, str):
        print("connect_error:" + str(data))
    if isinstance(data, dBError.dBError):
        print(data.code, data.source, data.message)

async def reconnect_error(data):
    if isinstance(data, str):
        print("reconnect_error:" + str(data))
    if isinstance(data, dBError.dBError):
        print(data.code, data.source, data.message)

async def reconnect_failed( data):
    print("reconnect_failed:", data)

async def reconnected():
    print("reconnected:")

async def rttpong(data=None):
    print("rttpong:", .dbridge.connectionstate.rttms)

async def disconnected():
    print("disconnected:")

async def connected():
    print("connected...")

try:
      dbridge.connectionstate.bind("connecting", connecting)
      dbridge.connectionstate.bind("reconnecting", reconnecting)
      dbridge.connectionstate.bind("connection_break", connection_break)
      dbridge.connectionstate.bind("state_change", state_change)
      dbridge.connectionstate.bind("connect_error", connect_error)
      dbridge.connectionstate.bind("reconnect_error", reconnect_error)
      dbridge.connectionstate.bind("reconnect_failed", reconnect_failed)
      dbridge.connectionstate.bind("reconnected", reconnected)
      dbridge.connectionstate.bind("rttpong", rttpong)
      dbridge.connectionstate.bind("connected", connected)
      dbridge.connectionstate.bind("disconnected", disconnected)
      
except Exception as e:
  	print(e.code, e.source, e.message)   
```
###### payload: `(dberror object)`

```python
{
    "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` is not a valid dataBridges application key. |
| DBLIB_CONNECT | INVALID_ACCESSTOKEN_FUNCTION |                                 | If *"callback function"* is not declared for authentication  **only** while using  **private, presence or system** channel/RPC functions. *(Check Channel or RPC section for details.)* |
| 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.)* |

#### 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"*. |

### Functions

#### 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. 

```python
# 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.
print(dbridge.connectionstate.rttms)

# To get the latest Latency in milliseconds between your application and the dataBridges router where your application is connected.
async def rttpong(self,  data=None):
 	print("rttpong:", data) 
    
try:
 	dbridge.connectionstate.bind("rttpong", rttpong)
except Exception as e:
 	print("source: {0} ,  code: {1}, message: {2}".format(e.source , e.code , e.message))

# Bind to rttpong, to get notified about the latest Latency in milliseconds between your application and the dataBridges router where your application is connected.
try:
 	dbridge.connectionstate.rttping()
except Exception as e:
 	print("source: {0} ,  code: {1}, message: {2}".format(e.source , e.code , e.message))
```

#### 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: .To subscribe to these type of channel. you will need to pass a trust-token when you subscribe to the channel. A trust-token is a JWT document created using a combination of channelname + sessionid + app.secret. 
  - 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. If the channel type is `pvt:,prs:,sys:`, dataBridges library will use the `access_token` function to get the access encrypted token and will use it for all communication with this channel.

| 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. <br />*e.g  channelName =* `mychannel` |
| Private      | **pvt:**channeName | Private channels is restricted channel. application will need to provide trust authorization token to subscribe and use Private channel. The dataBridges library will use the `access_token` function to get the trust authorization token. <br />*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. Since Presence channel is a specialized version of Private channel, application will need to provide trust authorization token to subscribe and use Private channels. The dataBridges library will use the `access_token` function to get the trust authorization token.<br />*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).  Since System channel is a specialized version of Presence channel, application will need to provide trust authorization token to subscribe and use Private channels. The dataBridges library will use the `access_token` function to get the trust authorization token.<br />*e.g  channelName =* `sys:systeminfo` |

dataBridges library provides 2 different ways to access any of above channel types based on usage.

| Channel Type         | Description                                                  |
| -------------------- | ------------------------------------------------------------ |
| Subscribe to Channel | application that subscribes to a channel will receive messages and can send messages. |
| Connect to Channel   | Where we have use-cases where application needs to only send messages and not interested to consume / receive channel messages, should connect to channel instead of subscribing to the channel. |

### Subscribe to Channel

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:

```python
try:
    subscribed_channel =  await dbridge.channel.subscribe('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)
```

| Parameter | Rules                                                        | Description                                     |
| --------- | ------------------------------------------------------------ | ----------------------------------------------- |
| `string`  | *channelName **OR**<br />**pvt:**channelName **OR**<br />**prs:**channelName **OR**<br />**sys:**channelName* | *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. Using this method application **cannot publish** any events.

```python
try:
    await dbridge.channel.subscribe('mychannel')
except dBError as e:
  	print(e.code, e.source, e.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 <br />1. *channelName* is not defined.<br />2. *channelName* validation error, `typeof()`  *channelName*  is not type string<br />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.

```python
try:
    dbridge.channel.unsubscribe('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)
```

| Parameter | Rules                                                        | Description                                        |
| --------- | ------------------------------------------------------------ | -------------------------------------------------- |
| `string`  | *channelName **OR**<br />**pvt:**channelName **OR**<br />**prs:**channelName **OR**<br />**sys:**channelName* | *channel*Name 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 | INVALID_CHANNEL_TYPE          | *channelName* is not subscribed, but it is in connected state. |
| DBLIB_CHANNEL_UNSUBSCRIBE | UNSUBSCRIBE_ALREADY_INITIATED | unsubscription to the channel is already initiated and hence the current unsubscribe command exited with exception. |

### Connect to Channel

Use-cases where application needs to only send channel messages and not interested to consume / receive channel messages, should connect to channel instead of subscribing to the channel.

#### connect()

The default method for connecting to a channel involves invoking the `channel.connect` function of your dataBridges object. Application cannot publish system events for which it has connected to. 

```python
try:
    connected_channel = dbridge.channel.connect('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)
```

| Parameter | Rules                                                        | Description                                   |
| --------- | ------------------------------------------------------------ | --------------------------------------------- |
| `string`  | *channelName **OR**<br />**pvt:**channelName **OR**<br />**prs:**channelName **OR**<br />**sys:**channelName* | *channel*Name to which connection to be done. |

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

##### Exceptions: 

| Source                | Code                      | Description                                                  |
| --------------------- | ------------------------- | ------------------------------------------------------------ |
| DBLIB_CHANNEL_CONNECT | NETWORK_DISCONNECTED      | Connection to dataBridges network is not active.             |
| DBLIB_CHANNEL_CONNECT | CHANNEL_ALREADY_CONNECTED | *channelName* is already connected.                          |
| DBLIB_CHANNEL_CONNECT | INVALID_CHANNELNAME       | Applicable for below conditions<br />1. *channelName* is not defined.<br />2. *channelName* validation error, `typeof()`  *channelName*  is not type string<br />3. *channelName* validation error, length of *channelName*  greater than **64**<br />4. *channelName* validation error, *channelName* fails `a-zA-Z0-9\.:_-` validation.<br />5. if *channelName* contains `:` and first token is not `pvt,prs,sys` |

#### disconnect() 

To disconnect from a connected channel, invoke the `disconnect` function of your dataBridges object. `disconnect` cannot be done on channel object.

```python
try:
    dbridge.channel.disconnect('mychannel')
except dBError as e:
  	print(e.code, e.source, e.message)
```
| Parameter | Rules                                                        | Description                                      |
| --------- | ------------------------------------------------------------ | ------------------------------------------------ |
| `string`  | *channelName **OR**<br />**pvt:**channelName **OR**<br />**prs:**channelName **OR**<br />**sys:**channelName* | *channel*Name to which disconnection to be done. |

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

##### Exceptions: 

| Source                   | Code                         | Description                                                  |
| ------------------------ | ---------------------------- | ------------------------------------------------------------ |
| DBLIB_CHANNEL_DISCONNECT | NETWORK_DISCONNECTED         | Connection to dataBridges network is not active.             |
| DBLIB_CHANNEL_DISCONNECT | DISCONNECT_ALREADY_INITIATED | disconnect to the channel is already initiated and hence the current disconnect command exited with exception. |
| DBLIB_CHANNEL_DISCONNECT | INVALID_CHANNEL              | *channelName* is not connected.                              |
| DBLIB_CHANNEL_DISCONNECT | INVALID_CHANNEL_TYPE         | *channelName* is not connected, but it is in subscribed state. |

### Channel Information

#### isOnline()

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

```python
isonline = dbridge.channel.isOnline('mychannel')
```

```python
isonline = subscribed_channel.isOnline()
```

| Parameter | Rules                                                        | Description   |
| --------- | ------------------------------------------------------------ | ------------- |
| `string`  | *channelName **OR**<br />**pvt:**channelName **OR**<br />**prs:**channelName **OR**<br />**sys:**channelName* | *channel*Name |

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

#### list()

<u>*dBridgeObject*</u>  provides a function to get list of successfully subscribed or connected channel. 

```python
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` **or** `connected`                   |
| `isonline` | *(boolean)* Is the current status of channel online or offline. |

#### getChannelName() 

*<u>channelObject</u>* provides a function to get the *channelName*. 

```python
chName = channelobject.getChannelName()  
```

| Return Type | Description                                       |
| ----------- | ------------------------------------------------- |
| `string`    | *channelName* of subscribed or connected channel. |

### Publish to Channel

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 driven processing flows

#### publish()

The default method for publishing to a channel involves invoking the `channel.publish` function of your *channelObject*. 

```python
try:
    channelObject.publish(eventname, payload, excludeSessionId, sourceId, seqno)
except dBError as e:
  	print(e.code, e.source, e.message) 

# Best practice is to check the channel is online before publishing any message.
if channelObject.isOnline():
 	try:
  		channelObject.publish(eventname, payload, excludeSessionId, sourceId, seqno)
 	except dBError as e:
    	print(e.code, e.source, e.message) 
```

| Parameter | Description                                                  |
| --------- | ------------------------------------------------------------ |
| `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.                |
| `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 | INVALID_SUBJECT      | Applicable for below conditions<br />1. *event* validation error, `typeof()`  *event*  is not type string<br />2.  *event* validation error,  *event*  is not defined |
| DBLIB_CHANNEL_PUBLISH | NETWORK_DISCONNECTED | Connection to dataBridges network is not active.             |

### Binding to events

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.

```python
# Binding to channel events on channelObject  
def eventFunction(payload ,  metadata):
  	print(payload , metadata)

try:
    channelObject.bind('eventName',  eventFunction)
except dBError as e:
  	print(e.code, e.source, e.message) 

# Binding to channel events on dbridgeObject 
try {
    dbridge.channel.bind('eventName', eventFunction)
except dBError as e:
  	print(e.code, e.source, e.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)`:

```python
{
    "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, specif