7
嘗試爲Python3支持的應用程序創建Web前端。該應用程序將需要雙向流媒體，這聽起來像是一個很好的機會來看待websockets。Python 3中的Websocket實現
我的第一個傾向是使用已經存在的東西，mod-pywebsocket的示例應用程序已被證明是有價值的。不幸的是，他們的API似乎不容易擴展，它是Python2。
環顧博客圈，許多人爲早期版本的websocket協議編寫了自己的websocket服務器，但大多數人並沒有實現安全密鑰哈希，所以不工作。
閱讀RFC 6455我決定去捅它自己，想出了以下內容：
#!/usr/bin/env python3
"""
A partial implementation of RFC 6455
http://tools.ietf.org/pdf/rfc6455.pdf
Brian Thorne 2012
"""
import socket
import threading
import time
import base64
import hashlib
def calculate_websocket_hash(key):
magic_websocket_string = b"258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
result_string = key + magic_websocket_string
sha1_digest = hashlib.sha1(result_string).digest()
response_data = base64.encodestring(sha1_digest)
response_string = response_data.decode('utf8')
return response_string
def is_bit_set(int_type, offset):
mask = 1 << offset
return not 0 == (int_type & mask)
def set_bit(int_type, offset):
return int_type | (1 << offset)
def bytes_to_int(data):
# note big-endian is the standard network byte order
return int.from_bytes(data, byteorder='big')
def pack(data):
"""pack bytes for sending to client"""
frame_head = bytearray(2)
# set final fragment
frame_head[0] = set_bit(frame_head[0], 7)
# set opcode 1 = text
frame_head[0] = set_bit(frame_head[0], 0)
# payload length
assert len(data) < 126, "haven't implemented that yet"
frame_head[1] = len(data)
# add data
frame = frame_head + data.encode('utf-8')
print(list(hex(b) for b in frame))
return frame
def receive(s):
"""receive data from client"""
# read the first two bytes
frame_head = s.recv(2)
# very first bit indicates if this is the final fragment
print("final fragment: ", is_bit_set(frame_head[0], 7))
# bits 4-7 are the opcode (0x01 -> text)
print("opcode: ", frame_head[0] & 0x0f)
# mask bit, from client will ALWAYS be 1
assert is_bit_set(frame_head[1], 7)
# length of payload
# 7 bits, or 7 bits + 16 bits, or 7 bits + 64 bits
payload_length = frame_head[1] & 0x7F
if payload_length == 126:
raw = s.recv(2)
payload_length = bytes_to_int(raw)
elif payload_length == 127:
raw = s.recv(8)
payload_length = bytes_to_int(raw)
print('Payload is {} bytes'.format(payload_length))
"""masking key
All frames sent from the client to the server are masked by a
32-bit nounce value that is contained within the frame
"""
masking_key = s.recv(4)
print("mask: ", masking_key, bytes_to_int(masking_key))
# finally get the payload data:
masked_data_in = s.recv(payload_length)
data = bytearray(payload_length)
# The ith byte is the XOR of byte i of the data with
# masking_key[i % 4]
for i, b in enumerate(masked_data_in):
data[i] = b^masking_key[i%4]
return data
def handle(s):
client_request = s.recv(4096)
# get to the key
for line in client_request.splitlines():
if b'Sec-WebSocket-Key:' in line:
key = line.split(b': ')[1]
break
response_string = calculate_websocket_hash(key)
header = '''HTTP/1.1 101 Switching Protocols\r
Upgrade: websocket\r
Connection: Upgrade\r
Sec-WebSocket-Accept: {}\r
\r
'''.format(response_string)
s.send(header.encode())
# this works
print(receive(s))
# this doesn't
s.send(pack('Hello'))
s.close()
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(('', 9876))
s.listen(1)
while True:
t,_ = s.accept()
threading.Thread(target=handle, args = (t,)).start()
使用這個基本的測試頁（與MOD-pywebsocket作品）：
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Web Socket Example</title>
<meta charset="UTF-8">
</head>
<body>
<div id="serveroutput"></div>
<form id="form">
<input type="text" value="Hello World!" id="msg" />
<input type="submit" value="Send" onclick="sendMsg()" />
</form>
<script>
var form = document.getElementById('form');
var msg = document.getElementById('msg');
var output = document.getElementById('serveroutput');
var s = new WebSocket("ws://"+window.location.hostname+":9876");
s.onopen = function(e) {
console.log("opened");
out('Connected.');
}
s.onclose = function(e) {
console.log("closed");
out('Connection closed.');
}
s.onmessage = function(e) {
console.log("got: " + e.data);
out(e.data);
}
form.onsubmit = function(e) {
e.preventDefault();
msg.value = '';
window.scrollTop = window.scrollHeight;
}
function sendMsg() {
s.send(msg.value);
}
function out(text) {
var el = document.createElement('p');
el.innerHTML = text;
output.appendChild(el);
}
msg.focus();
</script>
</body>
</html>
這會接收數據並將其正確掩蓋，但我無法使傳輸路徑正常工作。
作爲測試寫「你好」的插座，上面的程序計算出的字節將被寫入到所述插座爲：
['0x81', '0x5', '0x48', '0x65', '0x6c', '0x6c', '0x6f']
匹配其中在RFC的section 5.7給出的十六進制值。不幸的是，該框架在Chrome的開發者工具中從未出現過。
任何想法我失蹤？還是一個當前正在運行的Python3 websocket示例？
Tornado支持websockets和Python 3. http://www.tornadoweb.org/documentation/websocket.html –
謝謝托馬斯。我想首先有一個獨立的實現 - 這與理解協議和爲我解決問題一樣。看看[龍捲風源代碼]（https://github.com/facebook/tornado/blob/master/tornado/websocket.py），我看到一個頭部** Sec-WebSocket-Protocol **正在從服務器到客戶端，但[spec]（http://tools.ietf.org/html/rfc6455#section-4.2.2）表示這是可選的。 – Hardbyte
如果一個客戶端請求一個子協議，服務器需要回應它（總是假定它支持子協議）。不這樣做會導致握手錯誤，所以這可能與您的消息發送問題無關。 – simonc