html5 websocket connecting to python

Question

I am trying to connect a html5 websocket to python. I have two files:

1. index.html

<script>
      window.onload = function() {
        var connection = new WebSocket("ws://localhost:9876/");
        connection.onopen = function () { 
            connection.send('Ping');
        };

        connection.onerror = function (error) {
            console.log('WebSocket Error ' + error);
        };

        connection.onmessage = function (e) {
            console.log('Server: ' + e.data);
        };

      };
    </script>

2. server.py

import socket

HOST = ''
PORT = 9876
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(5)
conn, addr = s.accept()
print 'Connected by', addr
conn.send("Hello")
while 1:
    data = conn.recv(4096)
    print data
    if not data: break
    conn.sendall(data)
conn.close()

After starting server.py, it keeps running until I open index.html in my browser. When I do so, I get on the console the following:

WebSocket connection to 'ws://localhost:9876/' failed:
WebSocket Error [object Event]

However, on the other side(server.py) I get:

Connected by('127.0.0.1', 55460)GET / HTTP/1.1
Upgrade: websocket
Connection: Upgrade
Host: localhost:9876
Origin: null
Pragma: no-cache
Cache-Control: no-cache
Sec-WebSocket-Key: WP0GtT0hrdX1bKa0DepOHQ==
Sec-WebSocket-Version: 13
Sec-WebSocket-Extensions: x-webkit-deflate-frame
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.95 Safari/537.36

Q What's wrong with my codes? How should I modify it so as to have biorder communication between them? I am looking for something like this:

if data == 'kill': conn.close()

important edit

If I change in the index.html WebSocket("ws://localhost:9876/") to WebSocket("ws://html5rocks.websocket.org/echo") than it works. I guess that means that to problem is on the server.py side

clue #2

If I write WebSocket("ws://localhost/:9876") in the html, the python code cannot proceed the line conn, addr = s.accept()

While server.py is running, what happens when you telnet to the socket? telnet localhost 9876 — Mike Shultz
– Mike Shultz, Commented Aug 14, 2013 at 20:16
@Mike I am sorry but don't know where to enter the code above? — gen
– gen, Commented Aug 14, 2013 at 20:20
@gen tellnet is a shell (command prompt) command, not code. It just tries to make a connection to whatever address, give it a try and upload the results. — user1786283
– user1786283, Commented Aug 14, 2013 at 20:24
@enginefree I meant command not code, however my cmd doesn't recognise command 'telnet' — gen
– gen, Commented Aug 14, 2013 at 20:43
Your probably on windows. In which case you can try this, fettesps.com/windows-7-enable-telnet — user1786283
– user1786283, Commented Aug 14, 2013 at 20:44

mccakici · Accepted Answer · 2013-08-14 21:38:47Z

You haven't response headers. try ,

server.py

import socket, hashlib, base64, threading

class PyWSock:
    MAGIC = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
    HSHAKE_RESP = "HTTP/1.1 101 Switching Protocols\r\n" + \
                "Upgrade: websocket\r\n" + \
                "Connection: Upgrade\r\n" + \
                "Sec-WebSocket-Accept: %s\r\n" + \
                "\r\n"
    LOCK = threading.Lock()

    clients = []

    def recv_data (self, client):
        # as a simple server, we expect to receive:
        #    - all data at one go and one frame
        #    - one frame at a time
        #    - text protocol
        #    - no ping pong messages
        data = bytearray(client.recv(512))
        if(len(data) < 6):
            raise Exception("Error reading data")
        # FIN bit must be set to indicate end of frame
        assert(0x1 == (0xFF & data[0]) >> 7)
        # data must be a text frame
        # 0x8 (close connection) is handled with assertion failure
        assert(0x1 == (0xF & data[0]))

        # assert that data is masked
        assert(0x1 == (0xFF & data[1]) >> 7)
        datalen = (0x7F & data[1])

        #print("received data len %d" %(datalen,))

        str_data = ''
        if(datalen > 0):
            mask_key = data[2:6]
            masked_data = data[6:(6+datalen)]
            unmasked_data = [masked_data[i] ^ mask_key[i%4] for i in range(len(masked_data))]
            str_data = str(bytearray(unmasked_data))
        return str_data

    def broadcast_resp(self, data):
        # 1st byte: fin bit set. text frame bits set.
        # 2nd byte: no mask. length set in 1 byte. 
        resp = bytearray([0b10000001, len(data)])
        # append the data bytes
        for d in bytearray(data):
            resp.append(d)

        self.LOCK.acquire()
        for client in self.clients:
            try:
                client.send(resp)
            except:
                print("error sending to a client")
        self.LOCK.release()

    def parse_headers (self, data):
        headers = {}
        lines = data.splitlines()
        for l in lines:
            parts = l.split(": ", 1)
            if len(parts) == 2:
                headers[parts[0]] = parts[1]
        headers['code'] = lines[len(lines) - 1]
        return headers

    def handshake (self, client):
        print('Handshaking...')
        data = client.recv(2048)
        headers = self.parse_headers(data)
        print('Got headers:')
        for k, v in headers.iteritems():
            print k, ':', v

        key = headers['Sec-WebSocket-Key']
        resp_data = self.HSHAKE_RESP % ((base64.b64encode(hashlib.sha1(key+self.MAGIC).digest()),))
        print('Response: [%s]' % (resp_data,))
        return client.send(resp_data)

    def handle_client (self, client, addr):
        self.handshake(client)
        try:
            while 1:            
                data = self.recv_data(client)
                print("received [%s]" % (data,))
                self.broadcast_resp(data)
        except Exception as e:
            print("Exception %s" % (str(e)))
        print('Client closed: ' + str(addr))
        self.LOCK.acquire()
        self.clients.remove(client)
        self.LOCK.release()
        client.close()

    def start_server (self, port):
        s = socket.socket()
        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        s.bind(('', port))
        s.listen(5)
        while(1):
            print ('Waiting for connection...')
            conn, addr = s.accept()
            print ('Connection from: ' + str(addr))
            threading.Thread(target = self.handle_client, args = (conn, addr)).start()
            self.LOCK.acquire()
            self.clients.append(conn)
            self.LOCK.release()

ws = PyWSock()
ws.start_server(9876)

link

I think minimal server.py

import socket,hashlib,base64

MAGIC = '258EAFA5-E914-47DA-95CA-C5AB0DC85B11'
HSHAKE_RESP = "HTTP/1.1 101 Switching Protocols\r\n" + \
            "Upgrade: websocket\r\n" + \
            "Connection: Upgrade\r\n" + \
            "Sec-WebSocket-Accept: %s\r\n" + \
            "\r\n"

HOST = ''
PORT = 9876
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(5)
conn, addr = s.accept()
print 'Connected by', addr
data = conn.recv(4096)
headers = {}
lines = data.splitlines()
for l in lines:
    parts = l.split(": ", 1)
    if len(parts) == 2:
        headers[parts[0]] = parts[1]
headers['code'] = lines[len(lines) - 1]
key = headers['Sec-WebSocket-Key']
resp_data = HSHAKE_RESP % ((base64.b64encode(hashlib.sha1(key+MAGIC).digest()),))
conn.send(resp_data)

while 1:
    data = conn.recv(4096)
    if not data: 
        break
    databyte = bytearray(data)
    datalen = (0x7F & databyte[1])
    str_data = ''
    if(datalen > 0):
        mask_key = databyte[2:6]
        masked_data = databyte[6:(6+datalen)]
        unmasked_data = [masked_data[i] ^ mask_key[i%4] for i in range(len(masked_data))]
        str_data = str(bytearray(unmasked_data))
    print str_data
    resp = bytearray([0b10000001, len(str_data)])
    for d in bytearray(str_data):
        resp.append(d)
    conn.sendall(resp)
conn.close()

One time running. Because not threading.

Could you please tell me what makes it working, which i didn't have in my original code?
websocket is running request headers and response headers. Yours server code haven't response headers.
I am sorry, could you please explain me what response headers are?
you can see "print('Response: [%s]' % (resp_data,))", "HTTP/1.1 101 Switching Protocols\r\n" + \ "Upgrade: websocket\r\n" + \ "Connection: Upgrade\r\n" + \ "Sec-WebSocket-Accept: %s\r\n" + \ "\r\n"
Actually, as I cannot understand your code, I would like to reach the most simple code that still works. Could you please tell me which parts are the most important? I don't need encryption for instance.

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