WebSocket:WebSocket握手期间出错:发送非空"Sec-WebSocket-Protocol"标头但未收到响应

Question

我正在尝试与龙卷风服务器建立WS连接.服务器代码很简单:

class WebSocketHandler(tornado.websocket.WebSocketHandler):

    def open(self):
        print("WebSocket opened")

    def on_message(self, message):
        self.write_message(u"You said: " + message)

    def on_close(self):
        print("WebSocket closed")

def main():

    settings = {
        "static_path": os.path.join(os.path.dirname(__file__), "static")
    }


    app = tornado.web.Application([
            (r'/ws', WebSocketHandler),
            (r"/()$", tornado.web.StaticFileHandler, {'path':'static/index.html'}),
        ], **settings)


    app.listen(8888)
    tornado.ioloop.IOLoop.current().start()

我从这里复制粘贴客户端代码:

$(document).ready(function () {
    if ("WebSocket" in window) {

        console.log('WebSocket is supported by your browser.');

        var serviceUrl = 'ws://localhost:8888/ws';
        var protocol = 'Chat-1.0';
        var socket = new WebSocket(serviceUrl, protocol);

        socket.onopen = function () {
            console.log('Connection Established!');
        };

        socket.onclose = function () {
            console.log('Connection Closed!');
        };

        socket.onerror = function (error) {
            console.log('Error Occured: ' + error);
        };

        socket.onmessage = function (e) {
            if (typeof e.data === "string") {
                console.log('String message received: ' + e.data);
            }
            else if (e.data instanceof ArrayBuffer) {
                console.log('ArrayBuffer received: ' + e.data);
            }
            else if (e.data instanceof Blob) {
                console.log('Blob received: ' + e.data);
            }
        };

        socket.send("Hello WebSocket!");
        socket.close();
    }
});

当它尝试连接时,我在浏览器的控制台上获得以下输出:

WebSocket connection to 'ws://localhost:8888/ws' failed: Error during WebSocket handshake: Sent non-empty 'Sec-WebSocket-Protocol' header but no response was received

这是为什么？

Answer 1

正如whatwg.org的Websocket文档中指出的那样(它是标准草案的副本):

WebSocket(url,protocols)构造函数接受一个或两个参数.第一个参数url指定要连接的URL.第二种协议(如果存在)是字符串或字符串数​​组.如果它是一个字符串,它相当于一个只包含该字符串的数组; 如果省略,则相当于空数组.数组中的每个字符串都是子协议名称.仅当服务器报告已选择其中一个子协议时才建立连接.子协议名称必须都是符合WebSocket协议规范定义的包含Sec-WebSocket-Protocol字段值的元素要求的字符串.

您的服务器使用空Sec-WebSocket-Protocol标头应答websocket连接请求,因为它不支持子Chat-1协议.

由于您正在编写服务器端和客户端(除非您编写要分享的API),因此设置特定的子协议名称并不是非常重要.

您可以通过从javascript连接中删除子协议名称来解决此问题:

var socket = new WebSocket(serviceUrl);

或者通过修改服务器以支持所请求的协议.

我可以给出一个Ruby示例,但由于我没有足够的信息,所以我不能给出Python示例.

编辑(Ruby示例)

自从我在评论中被问到,这是一个Ruby示例.

此示例需要iodineHTTP/WebSockets服务器,因为它支持rack.upgrade规范草案(此处详述的概念)并添加了pub/sub API.

服务器代码可以通过终端执行,也可以作为config.ru文件中的Rack应用程序执行(从命令行运行iodine以启动服务器):

# frozen_string_literal: true

class ChatClient
  def on_open client
    @nickname = client.env['PATH_INFO'].to_s.split('/')[1] || "Guest"
    client.subscribe :chat    
    client.publish :chat , "#{@nickname} joined the chat."
    if client.env['my_websocket.protocol']
      client.write "You're using the #{client.env['my_websocket.protocol']} protocol"
    else
      client.write "You're not using a protocol, but we let it slide"
    end
  end
  def on_close client
    client.publish :chat , "#{@nickname} left the chat."
  end
  def on_message client, message
    client.publish :chat , "#{@nickname}: #{message}"
  end
end

module APP
  # the Rack application
  def self.call env
    return [200, {}, ["Hello World"]] unless env["rack.upgrade?"]
    env["rack.upgrade"] = ChatClient.new
    protocol = select_protocol(env)
    if protocol
      # we will use the same client for all protocols, because it's a toy example
      env['my_websocket.protocol'] = protocol # <= used by the client
      [101, { "Sec-Websocket-Protocol" => protocol }, []]
    else
      # we can either refuse the connection, or allow it without a match
      # here, it is allowed
      [101, {}, []]
    end
  end

  # the allowed protocols
  PROTOCOLS = %w{ chat-1.0 soap raw }

  def select_protocol(env)
    request_protocols = env["HTTP_SEC_WEBSOCKET_PROTOCOL"]
    unless request_protocols.nil?
      request_protocols = request_protocols.split(/,\s?/) if request_protocols.is_a?(String)
      request_protocols.detect { |request_protocol| PROTOCOLS.include? request_protocol }
    end # either `nil` or the result of `request_protocols.detect` are returned
  end

  # make functions available as a singleton module
  extend self
end

# config.ru
if __FILE__.end_with? ".ru"
  run APP 
else
# terminal?
  require 'iodine'
  Iodine.threads = 1
  Iodine.listen2http app: APP, log: true
  Iodine.start
end

要测试代码,以下JavaScript应该可以工作:

ws = new WebSocket("ws://localhost:3000/Mitchel", "chat-1.0");
ws.onmessage = function(e) { console.log(e.data); };
ws.onclose = function(e) { console.log("Closed"); };
ws.onopen = function(e) { e.target.send("Yo!"); };