---
schema_version: "1"
id: e505bc0328a1b96d002d990dcf0ac92d56c280e51c0ed4c67b7a4056d9d3db4a
title: WebSockets Server Components
collection: mulesoft
version: current
locale: en-us
portal_url: https://docs.salesforce.com/mulesoft/current/en-us/websockets-connector/latest/websockets-connector-server-components.md
canonical_url: https://docs.mulesoft.com/websockets-connector/latest/websockets-connector-server-components
source_site: docs.mulesoft.com
content_type: documentation
content_hash: 2af78aa1a150d2a465730ea88bcb31fe0aacc6f78565c2ff679d28c572636666
description: MuleSoft Documentation Site
release: "1.0"
latest: true
---
---
product: WebSockets Connector
version: 1.0
is-latest-version: true
---

# WebSockets Server Components

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

## Inbound Listener

The Inbound Listener component represents a WebSocket endpoint that clients can connect to. By
browsing to this endpoint, external clients establish a WebSocket connection, and trigger the flow
each time they send a message.

Clients can also indicate the default groups that this endpoint automatically subscribes to in the
defaultGroups parameter. If any broadcast operations are performed to these groups, this endpoint
receives and processes them. This subscription is done inside the app domain, which means that
adding the default groups parameter dows not send information about this subscription to the
outbound WebSocket counterparts. This is because the groups feature is not part of WS protocol. When
you subscribe an inbound WebSocket to a group, if one WebSocket within your app domain wants to send
a message to all other WebSockets, your app domain also has to be subscribed to the specified
groups. In short, group subscription only affects WebSockets residing in the same app domain, and
WebSockets from external applications are not subscribed by a Mule app to any other groups.

```xml
<flow name="onIncomingMessageFlow">
    <websocket:inbound-listener
        path="/chat"
        defaultGroups="#[['AVENGERS', 'REVENGERS']]"
        config-ref="ws" />
    <logger
        level="INFO"
        message="#['Received message ' ++ payload ++ ' from socket: ' ++ attributes.socketId]" />

    <websocket:send
        doc:name="SendResponse"
        socketId="#[attributes.socketId]"
        config-ref="ws" >
        <websocket:content>#['I'm fine, thank you!']</websocket:content>
    </websocket:send>
</flow>

<flow name="sendFriendlyMessageFlow">
    <websocket:open-outbound-socket path="/chat" config-ref="ws" />

    <websocket:send
        doc:name="SendMessage"
        socketId="#[attributes.socketId]"
        config-ref="ws" >
        <websocket:content>#['Hi! How are you?']</websocket:content>
    </websocket:send>
</flow>
```

## Send a Response

Unlike the `<http:listener>` element that automatically sends a response when a flow ends, this
component never automatically sends a response. This is because the WebSocket protocol is full
duplex and therefore provides no guarantee that you need to or want to send a response. Depending on
your use case, you might want to process the messages without sending a response, or only send
responses on certain cases.

If you want to send a response, use the `<websocket:send>` operation.

### Output

Each time a new message arrives, the flow triggers with a message, and the payload contains the
message’s content. The message’s MIME type is obtained from the `Content-Type` header of the HTTP
request. If the MIME type hasn’t been set, the MIME type defaults to one of the following depending
on the protocol’s DataFrame type:

- If binary, defaults MIME to `application/octect-stream`

- If text, defaults MIME to `text/plain`

The attributes contain a WebSockets attributes object.

## On Inbound Connection

This is a message source that triggers each time an INBOUND WebSockets connection is established.
You can only have one of these sources for a given path and it requires that a matching inbound
listener exist for the path. This is useful to perform post-connect tasks such as logging or
assigning the socket with a group.

This flow triggers synchronously. By the time this flow is invoked, the socket has already been
established and it could potentially be broadcasting or receiving messages. Those messages are
queued and not delivered to any flow until the event triggered by the source completes. If it fails,
all queued messages are discarded and the connection is dropped.

This message source has two main use cases:

- Keep track of the generated socket IDs for later use

- Have a validation point in which WebSockets can be rejected before it becomes usable to the
  application

For example, the following flow validates attributes from the originating request and decides to
close the connection if the validation doesn’t pass.

```xml
<flow name="onNewInboundConnection">
    <websocket:on-inbound-connection
        doc:name="On Inbound Connection"
        config-ref="WebSockets_Config"
        path="/chat"/>
    <choice doc:name="Choice" >
        <when expression="#[contains(attributes.headers.alias, 'admin')]">
            <websocket:close socketId="#[attributes.socketId]"
                reason="Cannot impersonate the admin"
                config-ref="WebSockets_Config"/>
        </when>
        <otherwise >
            <logger
                level="INFO"
                doc:name="Logger"
                message="Successfully connected to WebSocket #[attributes.socketId]" />
        </otherwise>
    </choice>
</flow>

<flow name="chat">
    <websocket:inbound-listener
        doc:name="Inbound listener"
        path="/chat"
        config-ref="WebSockets_Config"/>
    <logger
        level="INFO"
        doc:name="Logger"
        message="#['Received message' ++ payload]"/>
</flow>
```

## See Also

- [WebSockets Connector Overview](https://docs.mulesoft.com/websockets-connector/latest/)

- [Server Components](#)

- [Messaging Operations](https://docs.mulesoft.com/websockets-connector/latest/websockets-connector-messaging-operations)

- [Salesforce Help](https://help.salesforce.com)