WebSocket AT Commands

[中文]

Introduction

Important

The default AT firmware does not support the AT commands listed on this page. If you need ESP32 to support WebSocket commands, you can compile the ESP-AT project by following the steps in Compile ESP-AT Project Locally documentation. In the project configuration during the fifth step, make the following selections:

  • Enable Component config -> AT -> AT WebSocket command support

AT+WSCFG: Set the WebSocket Configuration

Set Command

Command:

AT+WSCFG=<link_id>,<ping_intv_sec>,<ping_timeout_sec>[,<buffer_size>]

Response:

OK

or

ERROR

Parameters

  • <link_id>: ID of the WebSocket connection. Range: [0,2], which means that AT can support up to three WebSocket connections.

  • <ping_intv_sec>: WebSocket Ping interval. Unit: second. Range: [1,7200]. Default: 10, which means that WebSocket Ping packets are sent every 10 seconds by default.

  • <ping_timeout_sec>: WebSocket Ping timeout. Unit: second. Range: [1,7200]. Default: 120, which means that by default, if the WebSocket Pong packet is not received within 120 seconds, the connection will be closed.

  • <buffer_size>: WebSocket buffer size. Unit: byte. Range: [1,8192]. Default: 1024.

Notes

  • This command should be configured before AT+WSOPEN command. Otherwise, it will not take effect.

Example

// Set the ping interval to 30 seconds, ping timeout to 60 seconds, and buffer size to 4096 bytes for link_id: 0.
AT+WSCFG=0,30,60,4096

AT+WSHEAD: Set/Query WebSocket Request Headers

Query Command

Command:

AT+WSHEAD?

Response:

+WSHEAD:<index>,<"req_header">

OK

Set Command

Command:

AT+WSHEAD=<req_header_len>

Response:

OK

>

The > symbol indicates that AT is ready to receive AT command data. At this point, you can enter the WebSocket request header (in the format of key: value). When the data length reaches the value of parameter <req_header_len>, AT returns:

OK

Parameters

  • <index>: Index value of WebSocket request header.

  • <”req_header”>: WebSocket request header.

  • <req_header_len>: WebSocket request header length. Unit: byte.

    • 0: Clear all set WebSocket request headers.

    • Other values: Set a new WebSocket request header.

Notes

  • This command can only set one WebSocket request header at a time, but it can be set multiple times to support multiple different WebSocket request headers.

  • The WebSocket request headers configured by this command are global. Once set, all WebSocket commands will carry these request headers.

Example

// Set the request header
AT+WSHEAD=49

// After receiving the ">" symbol, enter the authorization request header below.
AUTHORIZATION: Basic QTIzMzIyMDE5OTk6MTIzNDU2Nzg=

// Open a WebSocket connection
AT+WSOPEN=0,"wss://demo.piesocket.com/v3/channel_123?api_key=VCXCEuvhGcBDP7XhiJJUDvR1e1D3eiVjgZ9VRiaV&notify_self"

AT+WSOPEN: Query/Open a WebSocket Connection

Query Command

Command:

AT+WSOPEN?

Response:

When there is a connection, AT returns:

+WSOPEN:<link_id>,<state>,<"uri">

OK

When there is no connection, AT returns:

OK

Set Command

Command:

AT+WSOPEN=<link_id>,<"uri">[,<"subprotocol">][,<timeout_ms>][,<"auth">]

Response:

+WS_CONNECTED:<link_id>

OK

or

ERROR

Parameters

  • <link_id>: ID of the WebSocket connection. Range: [0,2], which means that AT can support up to three WebSocket connections.

  • <state>: The state of WebSocket connections.

    • 0: The WebSocket connection is closed.

    • 1: The WebSocket connection is reconnecting.

    • 2: The WebSocket connection is established.

    • 3: Receiving WebSocket Pong timeout or reading connection data error, waiting for reconnection.

    • 4: The WebSocket connection Received close frame from the server side and is sending close frame to the server.

  • <”uri”>: Uniform resource identifier of WebSocket server.

  • <”subprotocol”>: The subprotocol of WebSocket (refer to RFC6455 1.9 part for more details).

  • <timeout_ms>: Timeout for establishing a WebSocket connection. Unit: millisecond. Range: [0,180000]. Default: 15000.

  • <”auth”>: The authorization of WebSocket (refer to RFC6455 4.1.12 part for more details).

Example

// uri parameter comes from https://www.piesocket.com/websocket-tester
AT+WSOPEN=0,"wss://demo.piesocket.com/v3/channel_123?api_key=VCXCEuvhGcBDP7XhiJJUDvR1e1D3eiVjgZ9VRiaV&notify_self"

AT+WSSEND: Send Data to a WebSocket Connection

Set Command

Command:

AT+WSSEND=<link_id>,<length>[,<opcode>][,<timeout_ms>]

Response:

OK

>

This response indicates that AT is ready for receiving data from AT port. You should enter the data, and when the data length reaches the <length> value, the transmission of data starts.

If the connection cannot be established or is disrupted during data transmission, the system returns:

ERROR

If data is transmitted successfully, the system returns:

SEND OK

Parameters

  • <link_id>: ID of the WebSocket connection. Range: [0,2].

  • <length>: Length of data to send. Unit: byte. The maximum length that can be sent is determined by subtracting the value of <buffer_size> in AT+WSCFG <cmd-WSCFG> by 10 and the size of the heap space that the system can allocate (taking the smaller value of the two).

  • <opcode>: The opcode in the WebSocket frame sent. Range: [0,0xF]. Default: 1, which means text frame. For details about opcode, please refer to RFC6455 5.2 section.

    • 0x0: continuation frame

    • 0x1: text frame

    • 0x2: binary frame

    • 0x3 - 0x7: reserved for further non-control frames

    • 0x8: connection close frame

    • 0x9: ping frame

    • 0xA: pong frame

    • 0xB - 0xF: reserved for further control frames

  • <timeout_ms>: Send timeout. Unit: millisecond. Range: [0,60000]. Default: 10000.

AT+WSCLOSE: Close a WebSocket Connection

Set Command

Command:

AT+WSCLOSE=<link_id>

Response:

OK

Parameters

  • <link_id>: ID of the WebSocket connection. Range: [0,2].

Example

// Close the WebSocket connection whose link_id is 0
AT+WSCLOSE=0

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