WebSocket support for the ngx_lua module (and OpenResty)
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agentzh minor tweaks and improvements.
Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>
Latest commit 7152c22 Jun 28, 2018

README.markdown

Name

lua-resty-websocket - Lua WebSocket implementation for the ngx_lua module

Table of Contents

Status

This library is considered production ready.

Description

This Lua library implements a WebSocket server and client libraries based on the ngx_lua module.

This Lua library takes advantage of ngx_lua's cosocket API, which ensures 100% nonblocking behavior.

Note that only RFC 6455 is supported. Earlier protocol revisions like "hybi-10", "hybi-07", and "hybi-00" are not and will not be considered.

Synopsis

    local server = require "resty.websocket.server"

    local wb, err = server:new{
        timeout = 5000,  -- in milliseconds
        max_payload_len = 65535,
    }
    if not wb then
        ngx.log(ngx.ERR, "failed to new websocket: ", err)
        return ngx.exit(444)
    end

    local data, typ, err = wb:recv_frame()

    if not data then
        if not string.find(err, "timeout", 1, true) then
            ngx.log(ngx.ERR, "failed to receive a frame: ", err)
            return ngx.exit(444)
        end
    end

    if typ == "close" then
        -- for typ "close", err contains the status code
        local code = err

        -- send a close frame back:

        local bytes, err = wb:send_close(1000, "enough, enough!")
        if not bytes then
            ngx.log(ngx.ERR, "failed to send the close frame: ", err)
            return
        end
        ngx.log(ngx.INFO, "closing with status code ", code, " and message ", data)
        return
    end

    if typ == "ping" then
        -- send a pong frame back:

        local bytes, err = wb:send_pong(data)
        if not bytes then
            ngx.log(ngx.ERR, "failed to send frame: ", err)
            return
        end
    elseif typ == "pong" then
        -- just discard the incoming pong frame

    else
        ngx.log(ngx.INFO, "received a frame of type ", typ, " and payload ", data)
    end

    wb:set_timeout(1000)  -- change the network timeout to 1 second

    bytes, err = wb:send_text("Hello world")
    if not bytes then
        ngx.log(ngx.ERR, "failed to send a text frame: ", err)
        return ngx.exit(444)
    end

    bytes, err = wb:send_binary("blah blah blah...")
    if not bytes then
        ngx.log(ngx.ERR, "failed to send a binary frame: ", err)
        return ngx.exit(444)
    end

    local bytes, err = wb:send_close(1000, "enough, enough!")
    if not bytes then
        ngx.log(ngx.ERR, "failed to send the close frame: ", err)
        return
    end

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Modules

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resty.websocket.server

To load this module, just do this

    local server = require "resty.websocket.server"

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Methods

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new

syntax: wb, err = server:new()

syntax: wb, err = server:new(opts)

Performs the websocket handshake process on the server side and returns a WebSocket server object.

In case of error, it returns nil and a string describing the error.

An optional options table can be specified. The following options are as follows:

  • max_payload_len

    Specifies the maximal length of payload allowed when sending and receiving WebSocket frames.

  • send_masked

    Specifies whether to send out masked WebSocket frames. When it is true, masked frames are always sent. Default to false.

  • timeout

    Specifies the network timeout threshold in milliseconds. You can change this setting later via the set_timeout method call. Note that this timeout setting does not affect the HTTP response header sending process for the websocket handshake; you need to configure the send_timeout directive at the same time.

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set_timeout

syntax: wb:set_timeout(ms)

Sets the timeout delay (in milliseconds) for the network-related operations.

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send_text

syntax: bytes, err = wb:send_text(text)

Sends the text argument out as an unfragmented data frame of the text type. Returns the number of bytes that have actually been sent on the TCP level.

In case of errors, returns nil and a string describing the error.

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send_binary

syntax: bytes, err = wb:send_binary(data)

Sends the data argument out as an unfragmented data frame of the binary type. Returns the number of bytes that have actually been sent on the TCP level.

In case of errors, returns nil and a string describing the error.

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send_ping

syntax: bytes, err = wb:send_ping()

syntax: bytes, err = wb:send_ping(msg)

Sends out a ping frame with an optional message specified by the msg argument. Returns the number of bytes that have actually been sent on the TCP level.

In case of errors, returns nil and a string describing the error.

Note that this method does not wait for a pong frame from the remote end.

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send_pong

syntax: bytes, err = wb:send_pong()

syntax: bytes, err = wb:send_pong(msg)

Sends out a pong frame with an optional message specified by the msg argument. Returns the number of bytes that have actually been sent on the TCP level.

In case of errors, returns nil and a string describing the error.

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send_close

syntax: bytes, err = wb:send_close()

syntax: bytes, err = wb:send_close(code, msg)

Sends out a close frame with an optional status code and a message.

In case of errors, returns nil and a string describing the error.

For a list of valid status code, see the following document:

http://tools.ietf.org/html/rfc6455#section-7.4.1

Note that this method does not wait for a close frame from the remote end.

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send_frame

syntax: bytes, err = wb:send_frame(fin, opcode, payload)

Sends out a raw websocket frame by specifying the fin field (boolean value), the opcode, and the payload.

For a list of valid opcode, see

http://tools.ietf.org/html/rfc6455#section-5.2

In case of errors, returns nil and a string describing the error.

To control the maximal payload length allowed, you can pass the max_payload_len option to the new constructor.

To control whether to send masked frames, you can pass true to the send_masked option in the new constructor method. By default, unmasked frames are sent.

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recv_frame

syntax: data, typ, err = wb:recv_frame()

Receives a WebSocket frame from the wire.

In case of an error, returns two nil values and a string describing the error.

The second return value is always the frame type, which could be one of continuation, text, binary, close, ping, pong, or nil (for unknown types).

For close frames, returns 3 values: the extra status message (which could be an empty string), the string "close", and a Lua number for the status code (if any). For possible closing status codes, see

http://tools.ietf.org/html/rfc6455#section-7.4.1

For other types of frames, just returns the payload and the type.

For fragmented frames, the err return value is the Lua string "again".

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resty.websocket.client

To load this module, just do this

    local client = require "resty.websocket.client"

A simple example to demonstrate the usage:

    local client = require "resty.websocket.client"
    local wb, err = client:new()
    local uri = "ws://127.0.0.1:" .. ngx.var.server_port .. "/s"
    local ok, err = wb:connect(uri)
    if not ok then
        ngx.say("failed to connect: " .. err)
        return
    end

    local data, typ, err = wb:recv_frame()
    if not data then
        ngx.say("failed to receive the frame: ", err)
        return
    end

    ngx.say("received: ", data, " (", typ, "): ", err)

    local bytes, err = wb:send_text("copy: " .. data)
    if not bytes then
        ngx.say("failed to send frame: ", err)
        return
    end

    local bytes, err = wb:send_close()
    if not bytes then
        ngx.say("failed to send frame: ", err)
        return
    end

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Methods

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client:new

syntax: wb, err = client:new()

syntax: wb, err = client:new(opts)

Instantiates a WebSocket client object.

In case of error, it returns nil and a string describing the error.

An optional options table can be specified. The following options are as follows:

  • max_payload_len

    Specifies the maximal length of payload allowed when sending and receiving WebSocket frames.

  • send_unmasked

    Specifies whether to send out an unmasked WebSocket frames. When it is true, unmasked frames are always sent. Default to false. RFC 6455 requires, however, that the client MUST send masked frames to the server, so never set this option to true unless you know what you are doing.

  • timeout

    Specifies the default network timeout threshold in milliseconds. You can change this setting later via the set_timeout method call.

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client:connect

syntax: ok, err = wb:connect("ws://<host>:<port>/<path>")

syntax: ok, err = wb:connect("wss://<host>:<port>/<path>")

syntax: ok, err = wb:connect("ws://<host>:<port>/<path>", options)

syntax: ok, err = wb:connect("wss://<host>:<port>/<path>", options)

Connects to the remote WebSocket service port and performs the websocket handshake process on the client side.

Before actually resolving the host name and connecting to the remote backend, this method will always look up the connection pool for matched idle connections created by previous calls of this method.

An optional Lua table can be specified as the last argument to this method to specify various connect options:

  • protocols

    Specifies all the subprotocols used for the current WebSocket session. It could be a Lua table holding all the subprotocol names or just a single Lua string.

  • origin

    Specifies the value of the Origin request header.

  • pool

    Specifies a custom name for the connection pool being used. If omitted, then the connection pool name will be generated from the string template <host>:<port>.

  • ssl_verify

    Specifies whether to perform SSL certificate verification during the SSL handshake if the wss:// scheme is used.

The SSL connection mode (wss://) requires at least ngx_lua 0.9.11 or OpenResty 1.7.4.1.

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client:close

syntax: ok, err = wb:close()

Closes the current WebSocket connection. If no close frame is sent yet, then the close frame will be automatically sent.

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client:set_keepalive

syntax: ok, err = wb:set_keepalive(max_idle_timeout, pool_size)

Puts the current WebSocket connection immediately into the ngx_lua cosocket connection pool.

You can specify the max idle timeout (in ms) when the connection is in the pool and the maximal size of the pool every nginx worker process.

In case of success, returns 1. In case of errors, returns nil with a string describing the error.

Only call this method in the place you would have called the close method instead. Calling this method will immediately turn the current WebSocket object into the closed state. Any subsequent operations other than connect() on the current objet will return the closed error.

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client:set_timeout

syntax: wb:set_timeout(ms)

Identical to the set_timeout method of the resty.websocket.server objects.

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client:send_text

syntax: bytes, err = wb:send_text(text)

Identical to the send_text method of the resty.websocket.server objects.

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client:send_binary

syntax: bytes, err = wb:send_binary(data)

Identical to the send_binary method of the resty.websocket.server objects.

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client:send_ping

syntax: bytes, err = wb:send_ping()

syntax: bytes, err = wb:send_ping(msg)

Identical to the send_ping method of the resty.websocket.server objects.

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client:send_pong

syntax: bytes, err = wb:send_pong()

syntax: bytes, err = wb:send_pong(msg)

Identical to the send_pong method of the resty.websocket.server objects.

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client:send_close

syntax: bytes, err = wb:send_close()

syntax: bytes, err = wb:send_close(code, msg)

Identical to the send_close method of the resty.websocket.server objects.

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client:send_frame

syntax: bytes, err = wb:send_frame(fin, opcode, payload)

Identical to the send_frame method of the resty.websocket.server objects.

To control whether to send unmasked frames, you can pass true to the send_unmasked option in the new constructor method. By default, masked frames are sent.

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client:recv_frame

syntax: data, typ, err = wb:recv_frame()

Identical to the recv_frame method of the resty.websocket.server objects.

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resty.websocket.protocol

To load this module, just do this

    local protocol = require "resty.websocket.protocol"

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Methods

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recv_frame

syntax: data, typ, err = protocol.recv_frame(socket, max_payload_len, force_masking)

Receives a WebSocket frame from the wire.

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build_frame

syntax: frame = protocol.build_frame(fin, opcode, payload_len, payload, masking)

Builds a raw WebSocket frame.

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send_frame

syntax: bytes, err = protocol.send_frame(socket, fin, opcode, payload, max_payload_len, masking)

Sends a raw WebSocket frame.

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Automatic Error Logging

By default the underlying ngx_lua module does error logging when socket errors happen. If you are already doing proper error handling in your own Lua code, then you are recommended to disable this automatic error logging by turning off ngx_lua's lua_socket_log_errors directive, that is,

    lua_socket_log_errors off;

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Limitations

  • This library cannot be used in code contexts like init_by_lua*, set_by_lua*, log_by_lua*, and header_filter_by_lua* where the ngx_lua cosocket API is not available.
  • The resty.websocket object instance cannot be stored in a Lua variable at the Lua module level, because it will then be shared by all the concurrent requests handled by the same nginx worker process (see http://wiki.nginx.org/HttpLuaModule#Data_Sharing_within_an_Nginx_Worker ) and result in bad race conditions when concurrent requests are trying to use the same resty.websocket instance. You should always initiate resty.websocket objects in function local variables or in the ngx.ctx table. These places all have their own data copies for each request.

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Installation

It is recommended to use the latest OpenResty bundle directly where this library is bundled and enabled by default. At least OpenResty 1.4.2.9 is required. And you need to enable LuaJIT when building your OpenResty bundle by passing the --with-luajit option to its ./configure script. No extra Nginx configuration is required.

If you want to use this library with your own Nginx build (with ngx_lua), then you need to ensure you are using at least ngx_lua 0.9.0 (and lua-bitop library if you are not using LuaJIT). Also, You need to configure the lua_package_path directive to add the path of your lua-resty-websocket source tree to ngx_lua's Lua module search path, as in

    # nginx.conf
    http {
        lua_package_path "/path/to/lua-resty-websocket/lib/?.lua;;";
        ...
    }

and then load the library in Lua:

    local server = require "resty.websocket.server"

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TODO

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Community

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English Mailing List

The openresty-en mailing list is for English speakers.

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Chinese Mailing List

The openresty mailing list is for Chinese speakers.

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Bugs and Patches

Please report bugs or submit patches by

  1. creating a ticket on the GitHub Issue Tracker,
  2. or posting to the OpenResty community.

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Author

Yichun "agentzh" Zhang (章亦春) agentzh@gmail.com, OpenResty Inc.

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Copyright and License

This module is licensed under the BSD license.

Copyright (C) 2013-2017, by Yichun Zhang (agentzh) agentzh@gmail.com, OpenResty Inc.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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See Also

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