我正在尝试与我的 tornado 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 here 复制粘贴了客户端代码:

$(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得到以下输出:

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？

最佳答案

正如 whatwg.org's Websocket documentation 中指出的那样(这是标准草案的副本):

The WebSocket(url, protocols) constructor takes one or two arguments. The first argument, url, specifies the URL to which to connect. The second, protocols, if present, is either a string or an array of strings. If it is a string, it is equivalent to an array consisting of just that string; if it is omitted, it is equivalent to the empty array. Each string in the array is a subprotocol name. The connection will only be established if the server reports that it has selected one of these subprotocols. The subprotocol names must all be strings that match the requirements for elements that comprise the value of Sec-WebSocket-Protocol fields as defined by the WebSocket protocol specification.

您的服务器使用空的 Sec-WebSocket-Protocol header 响应 websocket 连接请求，因为它不支持 Chat-1 子协议(protocol)。

由于您正在编写服务器端和客户端(除非您编写的 API 是您打算共享的)，因此设置特定的子协议(protocol)名称应该不是特别重要。

您可以通过从 javascript 连接中删除子协议(protocol)名称来解决此问题:

var socket = new WebSocket(serviceUrl);

或者修改您的服务器以支持所请求的协议(protocol)。

我可以举一个 Ruby 的例子，但我不能举一个 Python 的例子，因为我没有足够的信息。

编辑(Ruby 示例)

由于我在评论中被问到，这里有一个 Ruby 示例。

此示例需要 iodine HTTP/WebSockets 服务器，因为它支持 rack.upgrade specification draft (概念详细 here )并添加了发布/订阅 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!"); };

关于python - WebSocket:WebSocket 握手期间出错:已发送非空 'Sec-WebSocket-Protocol' header 但未收到响应，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/34198566/