Python 的 Socket 编程教程

喜欢ヅ旅行 2022-04-21 16:22 194阅读 0赞

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   <td> <h1><a href="http://www.pythonfan.org/thread-6505-1-1.html" rel="nofollow">Python 的 Socket 编程教程</a></h1> <span><a href="http://www.pythonfan.org/thread-6505-1-1.html" title="您的朋友访问此链接后，您将获得相应的积分奖励" rel="nofollow">[复制链接]</a></span> 
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           <em>发表于 2012-11-10 14:56:10</em> 
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               <td>这是用来快速学习 Python Socket 套接字编程的指南和教程。Python 的 Socket 编程跟 C 语言很像。&nbsp;&nbsp;Python 官方关于 Socket 的函数请看 <a href="http://docs.python.org/library/socket.html" rel="nofollow"><span style="color:#0066cc">http://docs.python.org/library/socket.html</span></a> <br> 基本上，Socket 是任何一种计算机网络通讯中最基础的内容。例如当你在浏览器地址栏中输入 <a href="http://www.oschina.net" rel="nofollow"> www.oschina.net</a> 时，你会打开一个套接字，然后连接到 <a href="http://www.oschina.net" rel="nofollow"> www.oschina.net</a> 并读取响应的页面然后然后显示出来。而其他一些聊天客户端如 gtalk 和 skype 也是类似。任何网络通讯都是通过 Socket 来完成的。 <br> <strong>写在开头 </strong>本教程假设你已经有一些基本的 Python 编程的知识。 <br> 让我们开始 Socket 编程吧。 <br> <strong>创建 Socket </strong>首先要做的就是创建一个 Socket，socket 的 socket 函数可以实现，代码如下： 
                <div> 
                 <div> 
                  <ol> 
                   <li>#Socket client example in python<br> </li> 
                   <li><br> </li> 
                   <li>import socket&nbsp; &nbsp; &nbsp; &nbsp; #for sockets<br> </li> 
                   <li><br> </li> 
                   <li>#create an AF_INET, STREAM socket (TCP)<br> </li> 
                   <li>s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li><br> </li> 
                   <li>print 'Socket Created'</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 函数 socket.socket 创建了一个 Socket，并返回 Socket 的描述符可用于其他 Socket 相关的函数。 <br> 上述代码使用了下面两个属性来创建 Socket： <br> 地址簇 : AF_INET (IPv4)<br> 类型: SOCK_STREAM (使用 TCP 传输控制协议) <br> <strong>错误处理</strong> <br> 如果 socket 函数失败了，python 将抛出一个名为 socket.error 的异常，这个异常必须予以处理： 
                <div> 
                 <div> 
                  <ol> 
                   <li>#handling errors in python socket programs<br> </li> 
                   <li><br> </li> 
                   <li>import socket&nbsp; &nbsp; &nbsp; &nbsp; #for sockets<br> </li> 
                   <li>import sys&nbsp; &nbsp; &nbsp; &nbsp; #for exit<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #create an AF_INET, STREAM socket (TCP)<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>except socket.error, msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Failed to create socket. Error code: ' + str(msg[0]) + ' , Error message : ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit();<br> </li> 
                   <li><br> </li> 
                   <li>print 'Socket Created'</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 好了，假设你已经成功创建了 Socket，下一步该做什么呢？接下来我们将使用这个 Socket 来连接到服务器。 <br> <strong>注意</strong> <br> 与 SOCK_STREAM 相对应的其他类型是 SOCK_DGRAM 用于 UDP 通讯协议，UDP 通讯是非连接 Socket，在这篇文章中我们只讨论 SOCK_STREAM ，或者叫 TCP 。 <br> <strong>连接到服务器 </strong>连接到服务器需要服务器地址和端口号，这里使用的是 <a href="http://www.oschina.net" rel="nofollow"> www.oschina.net</a> 和 80 端口。 <br> <strong>首先获取远程主机的 IP 地址</strong> <br> 连接到远程主机之前，我们需要知道它的 IP 地址，在 Python 中，获取 IP 地址是很简单的： 
                <div> 
                 <div> 
                  <ol> 
                   <li>import socket&nbsp; &nbsp; &nbsp; &nbsp; #for sockets<br> </li> 
                   <li>import sys&nbsp; &nbsp; &nbsp; &nbsp; #for exit<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #create an AF_INET, STREAM socket (TCP)<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>except socket.error, msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Failed to create socket. Error code: ' + str(msg[0]) + ' , Error message : ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit();<br> </li> 
                   <li><br> </li> 
                   <li>print 'Socket Created'<br> </li> 
                   <li><br> </li> 
                   <li>host = 'www.oschina.net'<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; remote_ip = socket.gethostbyname( host )<br> </li> 
                   <li><br> </li> 
                   <li>except socket.gaierror:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #could not resolve<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Hostname could not be resolved. Exiting'<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Ip address of ' + host + ' is ' + remote_ip</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 我们已经有 IP 地址了，接下来需要指定要连接的端口。 <br> 代码： 
                <div> 
                 <div> 
                  <ol> 
                   <li>import socket&nbsp; &nbsp; &nbsp; &nbsp; #for sockets<br> </li> 
                   <li>import sys&nbsp; &nbsp; &nbsp; &nbsp; #for exit<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #create an AF_INET, STREAM socket (TCP)<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>except socket.error, msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Failed to create socket. Error code: ' + str(msg[0]) + ' , Error message : ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit();<br> </li> 
                   <li><br> </li> 
                   <li>print 'Socket Created'<br> </li> 
                   <li><br> </li> 
                   <li>host = 'www.oschina.net'<br> </li> 
                   <li>port = 80<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; remote_ip = socket.gethostbyname( host )<br> </li> 
                   <li><br> </li> 
                   <li>except socket.gaierror:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #could not resolve<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Hostname could not be resolved. Exiting'<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Ip address of ' + host + ' is ' + remote_ip<br> </li> 
                   <li><br> </li> 
                   <li>#Connect to remote server<br> </li> 
                   <li>s.connect((remote_ip , port))<br> </li> 
                   <li><br> </li> 
                   <li>print 'Socket Connected to ' + host + ' on ip ' + remote_ip</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 现在运行程序 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ python client.py<br> </li> 
                   <li>Socket Created<br> </li> 
                   <li>Ip address of www.oschina.net is 61.145.122.155<br> </li> 
                   <li>Socket Connected to www.oschina.net on ip 61.145.122.155</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 这段程序创建了一个 Socket 并进行连接，试试使用其他一些不存在的端口（如81）会是怎样？这个逻辑相当于构建了一个端口扫描器。 <br> 已经连接上了，接下来就是往服务器上发送数据。 <br> <strong>免费提示</strong> <br> 使用 SOCK_STREAM/TCP 套接字才有“连接”的概念。连接意味着可靠的数据流通讯机制，可以同时有多个数据流。可以想象成一个数据互不干扰的管道。另外一个重要的提示是：数据包的发送和接收是有顺序的。 <br> 其他一些 Socket 如 UDP、ICMP 和 ARP 没有“连接”的概念，它们是无连接通讯，意味着你可从任何人或者给任何人发送和接收数据包。 <br> <strong>发送数据<br> </strong>sendall 函数用于简单的发送数据，我们来向 oschina 发送一些数据： 
                <div> 
                 <div> 
                  <ol> 
                   <li>import socket&nbsp; &nbsp; &nbsp; &nbsp; #for sockets<br> </li> 
                   <li>import sys&nbsp; &nbsp; &nbsp; &nbsp; #for exit<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #create an AF_INET, STREAM socket (TCP)<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>except socket.error, msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Failed to create socket. Error code: ' + str(msg[0]) + ' , Error message : ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit();<br> </li> 
                   <li><br> </li> 
                   <li>print 'Socket Created'<br> </li> 
                   <li><br> </li> 
                   <li>host = 'www.oschina.net'<br> </li> 
                   <li>port = 80<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; remote_ip = socket.gethostbyname( host )<br> </li> 
                   <li><br> </li> 
                   <li>except socket.gaierror:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #could not resolve<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Hostname could not be resolved. Exiting'<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Ip address of ' + host + ' is ' + remote_ip<br> </li> 
                   <li><br> </li> 
                   <li>#Connect to remote server<br> </li> 
                   <li>s.connect((remote_ip , port))<br> </li> 
                   <li><br> </li> 
                   <li>print 'Socket Connected to ' + host + ' on ip ' + remote_ip<br> </li> 
                   <li><br> </li> 
                   <li>#Send some data to remote server<br> </li> 
                   <li>message = "GET / HTTP/1.1\r\n\r\n"<br> </li> 
                   <li><br> </li> 
                   <li>try :<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #Set the whole string<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s.sendall(message)<br> </li> 
                   <li>except socket.error:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #Send failed<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Send failed'<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li><br> </li> 
                   <li>print 'Message send successfully'</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 上述例子中，首先连接到目标服务器，然后发送字符串数据 "GET / HTTP/1.1\r\n\r\n" ，这是一个 HTTP 协议的命令，用来获取网站首页的内容。 <br> 接下来需要读取服务器返回的数据。 <br> <strong>接收数据 </strong>recv 函数用于从 socket 接收数据： 
                <div> 
                 <div> 
                  <ol> 
                   <li>#Socket client example in python<br> </li> 
                   <li><br> </li> 
                   <li>import socket&nbsp; &nbsp; &nbsp; &nbsp; #for sockets<br> </li> 
                   <li>import sys&nbsp; &nbsp; &nbsp; &nbsp; #for exit<br> </li> 
                   <li><br> </li> 
                   <li>#create an INET, STREAMing socket<br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>except socket.error:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Failed to create socket'<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Socket Created'<br> </li> 
                   <li><br> </li> 
                   <li>host = 'oschina.net';<br> </li> 
                   <li>port = 80;<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; remote_ip = socket.gethostbyname( host )<br> </li> 
                   <li><br> </li> 
                   <li>except socket.gaierror:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #could not resolve<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Hostname could not be resolved. Exiting'<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li><br> </li> 
                   <li>#Connect to remote server<br> </li> 
                   <li>s.connect((remote_ip , port))<br> </li> 
                   <li><br> </li> 
                   <li>print 'Socket Connected to ' + host + ' on ip ' + remote_ip<br> </li> 
                   <li><br> </li> 
                   <li>#Send some data to remote server<br> </li> 
                   <li>message = "GET / HTTP/1.1\r\nHost: oschina.net\r\n\r\n"<br> </li> 
                   <li><br> </li> 
                   <li>try :<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #Set the whole string<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s.sendall(message)<br> </li> 
                   <li>except socket.error:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #Send failed<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Send failed'<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li><br> </li> 
                   <li>print 'Message send successfully'<br> </li> 
                   <li><br> </li> 
                   <li>#Now receive data<br> </li> 
                   <li>reply = s.recv(4096)<br> </li> 
                   <li><br> </li> 
                   <li>print reply</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 下面是上述程序执行的结果： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ python client.py<br> </li> 
                   <li>Socket Created<br> </li> 
                   <li>Ip address of oschina.net is 61.145.122.<br> </li> 
                   <li>Socket Connected to oschina.net on ip 61.145.122.155<br> </li> 
                   <li>Message send successfully<br> </li> 
                   <li>HTTP/1.1 301 Moved Permanently<br> </li> 
                   <li>Server: nginx<br> </li> 
                   <li>Date: Wed, 24 Oct 2012 13:26:46 GMT<br> </li> 
                   <li>Content-Type: text/html<br> </li> 
                   <li>Content-Length: 178<br> </li> 
                   <li>Connection: keep-alive<br> </li> 
                   <li>Keep-Alive: timeout=20<br> </li> 
                   <li>Location: http://www.oschina.net/</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> oschina.net 回应了我们所请求的 URL 的内容，很简单。数据接收完了，可以关闭 Socket 了。 <br> <strong>关闭 socket </strong>close 函数用于关闭 Socket： 
                <div> 
                 <div> 
                  <ol> 
                   <li>s.close()</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 这就是了。 <br> <strong>让我们回顾一下 </strong>上述的示例中我们学到了如何： <br> 1. 创建 Socket<br> 2. 连接到远程服务器<br> 3. 发送数据<br> 4. 接收回应 <br> 当你用浏览器打开 <a href="http://www.oschina.net" rel="nofollow">www.oschina.net</a> 时，其过程也是一样。包含两种类型，分别是客户端和服务器，客户端连接到服务器并读取数据，服务器使用 Socket 接收进入的连接并提供数据。因此在这里 <a href="http://www.oschina.net" rel="nofollow">www.oschina.net</a> 是服务器端，而你的浏览器是客户端。 <br> 接下来我们开始在服务器端做点编码。 <br> <strong>服务器端编程 </strong>服务器端编程主要包括下面几步： <br> 1. 打开 socket<br> 2. 绑定到一个地址和端口<br> 3. 侦听进来的连接<br> 4. 接受连接<br> 5. 读写数据 <br> 我们已经学习过如何打开 Socket 了，下面是绑定到指定的地址和端口上。 <br> <strong>绑定 Socket </strong>bind 函数用于将 Socket 绑定到一个特定的地址和端口，它需要一个类似 connect 函数所需的 sockaddr_in 结构体。 <br> 示例代码： 
                <div> 
                 <div> 
                  <ol> 
                   <li>import socket<br> </li> 
                   <li>import sys<br> </li> 
                   <li><br> </li> 
                   <li>HOST = ''&nbsp; &nbsp; &nbsp; &nbsp; # Symbolic name meaning all available interfaces<br> </li> 
                   <li>PORT = 8888&nbsp; &nbsp; &nbsp; &nbsp; # Arbitrary non-privileged port<br> </li> 
                   <li><br> </li> 
                   <li>s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>print 'Socket created'<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s.bind((HOST, PORT))<br> </li> 
                   <li>except socket.error , msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Socket bind complete'</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 绑定完成后，就需要让 Socket 开始侦听连接。很显然，你不能将两个不同的 Socket 绑定到同一个端口之上。 <br> <strong>连接侦听 </strong>绑定 Socket 之后就可以开始侦听连接，我们需要将 Socket 变成侦听模式。socket 的 listen 函数用于实现侦听模式： 
                <div> 
                 <div> 
                  <ol> 
                   <li>s.listen(10)<br> </li> 
                   <li>print 'Socket now listening'</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> listen 函数所需的参数成为 backlog，用来控制程序忙时可保持等待状态的连接数。这里我们传递的是 10，意味着如果已经有 10 个连接在等待处理，那么第 11 个连接将会被拒绝。当检查了 socket_accept 后这个会更加清晰。 <br> <strong>接受连接 </strong>示例代码： 
                <div> 
                 <div> 
                  <ol> 
                   <li>import socket<br> </li> 
                   <li>import sys<br> </li> 
                   <li><br> </li> 
                   <li>HOST = ''&nbsp; &nbsp; &nbsp; &nbsp; # Symbolic name meaning all available interfaces<br> </li> 
                   <li>PORT = 8888&nbsp; &nbsp; &nbsp; &nbsp; # Arbitrary non-privileged port<br> </li> 
                   <li><br> </li> 
                   <li>s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>print 'Socket created'<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s.bind((HOST, PORT))<br> </li> 
                   <li>except socket.error , msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Socket bind complete'<br> </li> 
                   <li><br> </li> 
                   <li>s.listen(10)<br> </li> 
                   <li>print 'Socket now listening'<br> </li> 
                   <li><br> </li> 
                   <li>#wait to accept a connection - blocking call<br> </li> 
                   <li>conn, addr = s.accept()<br> </li> 
                   <li><br> </li> 
                   <li>#display client information<br> </li> 
                   <li>print 'Connected with ' + addr[0] + ':' + str(addr[1])</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> <strong>输出</strong> <br> 运行该程序将会显示： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ python server.py<br> </li> 
                   <li>Socket created<br> </li> 
                   <li>Socket bind complete<br> </li> 
                   <li>Socket now listening</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 现在这个程序开始等待连接进入，端口是 8888，请不要关闭这个程序，我们来通过 telnet 程序来进行测试。 <br> 打开命令行窗口并输入： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ telnet localhost 8888<br> </li> 
                   <li><br> </li> 
                   <li>It will immediately show<br> </li> 
                   <li>$ telnet localhost 8888<br> </li> 
                   <li>Trying 127.0.0.1...<br> </li> 
                   <li>Connected to localhost.<br> </li> 
                   <li>Escape character is '^]'.<br> </li> 
                   <li>Connection closed by foreign host.</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 而服务器端窗口显示的是： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ python server.py<br> </li> 
                   <li>Socket created<br> </li> 
                   <li>Socket bind complete<br> </li> 
                   <li>Socket now listening<br> </li> 
                   <li>Connected with 127.0.0.1:59954</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 我们可看到客户端已经成功连接到服务器。 <br> 上面例子我们接收到连接并立即关闭，这样的程序没什么实际的价值，连接建立后一般会有大量的事情需要处理，因此让我们来给客户端做出点回应吧。 <br> sendall 函数可通过 Socket 给客户端发送数据： 
                <div> 
                 <div> 
                  <ol> 
                   <li>import socket<br> </li> 
                   <li>import sys<br> </li> 
                   <li><br> </li> 
                   <li>HOST = ''&nbsp; &nbsp; &nbsp; &nbsp; # Symbolic name meaning all available interfaces<br> </li> 
                   <li>PORT = 8888&nbsp; &nbsp; &nbsp; &nbsp; # Arbitrary non-privileged port<br> </li> 
                   <li><br> </li> 
                   <li>s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>print 'Socket created'<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s.bind((HOST, PORT))<br> </li> 
                   <li>except socket.error , msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Socket bind complete'<br> </li> 
                   <li><br> </li> 
                   <li>s.listen(10)<br> </li> 
                   <li>print 'Socket now listening'<br> </li> 
                   <li><br> </li> 
                   <li>#wait to accept a connection - blocking call<br> </li> 
                   <li>conn, addr = s.accept()<br> </li> 
                   <li><br> </li> 
                   <li>print 'Connected with ' + addr[0] + ':' + str(addr[1])<br> </li> 
                   <li><br> </li> 
                   <li>#now keep talking with the client<br> </li> 
                   <li>data = conn.recv(1024)<br> </li> 
                   <li>conn.sendall(data)<br> </li> 
                   <li><br> </li> 
                   <li>conn.close()<br> </li> 
                   <li>s.close()</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 继续运行上述代码，然后打开另外一个命令行窗口输入下面命令： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ telnet localhost 8888<br> </li> 
                   <li>Trying 127.0.0.1...<br> </li> 
                   <li>Connected to localhost.<br> </li> 
                   <li>Escape character is '^]'.<br> </li> 
                   <li>happy<br> </li> 
                   <li>happy<br> </li> 
                   <li>Connection closed by foreign host.</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 可看到客户端接收到来自服务器端的回应内容。 <br> 上面的例子还是一样，服务器端回应后就立即退出了。而一些真正的服务器像 <a href="http://www.oschina.net" rel="nofollow"> www.oschina.net</a> 是一直在运行的，时刻接受连接请求。 <br> 也就是说服务器端应该一直处于运行状态，否则就不能成为“服务”，因此我们要让服务器端一直运行，最简单的方法就是把 accept 方法放在一个循环内。 <br> <strong>一直在运行的服务器 </strong>对上述代码稍作改动： 
                <div> 
                 <div> 
                  <ol> 
                   <li>import socket<br> </li> 
                   <li>import sys<br> </li> 
                   <li><br> </li> 
                   <li>HOST = ''&nbsp; &nbsp; &nbsp; &nbsp; # Symbolic name meaning all available interfaces<br> </li> 
                   <li>PORT = 8888&nbsp; &nbsp; &nbsp; &nbsp; # Arbitrary non-privileged port<br> </li> 
                   <li><br> </li> 
                   <li>s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>print 'Socket created'<br> </li> 
                   <li><br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s.bind((HOST, PORT))<br> </li> 
                   <li>except socket.error , msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Socket bind complete'<br> </li> 
                   <li><br> </li> 
                   <li>s.listen(10)<br> </li> 
                   <li>print 'Socket now listening'<br> </li> 
                   <li><br> </li> 
                   <li>#now keep talking with the client<br> </li> 
                   <li>while 1:<br> </li> 
                   <li>&nbsp; &nbsp; #wait to accept a connection - blocking call<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; conn, addr = s.accept()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Connected with ' + addr[0] + ':' + str(addr[1])<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; data = conn.recv(1024)<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; reply = 'OK...' + data<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; if not data: <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; break<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; conn.sendall(reply)<br> </li> 
                   <li><br> </li> 
                   <li>conn.close()<br> </li> 
                   <li>s.close()</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 很简单只是加多一个 while 1 语句而已。 <br> 继续运行服务器，然后打开另外三个命令行窗口。每个窗口都使用 telnet 命令连接到服务器： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ telnet localhost 5000<br> </li> 
                   <li>Trying 127.0.0.1...<br> </li> 
                   <li>Connected to localhost.<br> </li> 
                   <li>Escape character is '^]'.<br> </li> 
                   <li>happy<br> </li> 
                   <li>OK .. happy<br> </li> 
                   <li>Connection closed by foreign host.</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 服务器所在的终端窗口显示的是： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ python server.py<br> </li> 
                   <li>Socket created<br> </li> 
                   <li>Socket bind complete<br> </li> 
                   <li>Socket now listening<br> </li> 
                   <li>Connected with 127.0.0.1:60225<br> </li> 
                   <li>Connected with 127.0.0.1:60237<br> </li> 
                   <li>Connected with 127.0.0.1:60239</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 你看服务器再也不退出了，好吧，用 Ctrl+C 关闭服务器，所有的 telnet 终端将会显示 "Connection closed by foreign host." <br> 已经很不错了，但是这样的通讯效率太低了，服务器程序使用循环来接受连接并发送回应，这相当于是一次最多处理一个客户端的请求，而我们要求服务器可同时处理多个请求。 <br> <strong>处理多个连接 </strong>为了处理多个连接，我们需要一个独立的处理代码在主服务器接收到连接时运行。一种方法是使用线程，服务器接收到连接然后创建一个线程来处理连接收发数据，然后主服务器程序返回去接收新的连接。 <br> 下面是我们使用线程来处理连接请求： 
                <div> 
                 <div> 
                  <ol> 
                   <li>import socket<br> </li> 
                   <li>import sys<br> </li> 
                   <li>from thread import *<br> </li> 
                   <li><br> </li> 
                   <li>HOST = ''&nbsp; &nbsp; &nbsp; &nbsp; # Symbolic name meaning all available interfaces<br> </li> 
                   <li>PORT = 8888&nbsp; &nbsp; &nbsp; &nbsp; # Arbitrary non-privileged port<br> </li> 
                   <li><br> </li> 
                   <li>s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)<br> </li> 
                   <li>print 'Socket created'<br> </li> 
                   <li><br> </li> 
                   <li>#Bind socket to local host and port<br> </li> 
                   <li>try:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; s.bind((HOST, PORT))<br> </li> 
                   <li>except socket.error , msg:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; sys.exit()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>print 'Socket bind complete'<br> </li> 
                   <li><br> </li> 
                   <li>#Start listening on socket<br> </li> 
                   <li>s.listen(10)<br> </li> 
                   <li>print 'Socket now listening'<br> </li> 
                   <li><br> </li> 
                   <li>#Function for handling connections. This will be used to create threads<br> </li> 
                   <li>def clientthread(conn):<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #Sending message to connected client<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; conn.send('Welcome to the server. Type something and hit enter\n') #send only takes string<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #infinite loop so that function do not terminate and thread do not end.<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; while True:<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; #Receiving from client<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; data = conn.recv(1024)<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; reply = 'OK...' + data<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if not data: <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; break<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; conn.sendall(reply)<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #came out of loop<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; conn.close()<br> </li> 
                   <li><br> </li> 
                   <li>#now keep talking with the client<br> </li> 
                   <li>while 1:<br> </li> 
                   <li>&nbsp; &nbsp; #wait to accept a connection - blocking call<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; conn, addr = s.accept()<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; print 'Connected with ' + addr[0] + ':' + str(addr[1])<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; <br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; #start new thread takes 1st argument as a function name to be run, second is the tuple of arguments to the function.<br> </li> 
                   <li>&nbsp; &nbsp; &nbsp; &nbsp; start_new_thread(clientthread ,(conn,))<br> </li> 
                   <li><br> </li> 
                   <li>s.close()</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 运行上述服务端程序，然后像之前一样打开三个终端窗口并执行 telent 命令： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ telnet localhost 8888<br> </li> 
                   <li>Trying 127.0.0.1...<br> </li> 
                   <li>Connected to localhost.<br> </li> 
                   <li>Escape character is '^]'.<br> </li> 
                   <li>Welcome to the server. Type something and hit enter<br> </li> 
                   <li>hi<br> </li> 
                   <li>OK...hi<br> </li> 
                   <li>asd<br> </li> 
                   <li>OK...asd<br> </li> 
                   <li>cv<br> </li> 
                   <li>OK...cv</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 服务器端所在终端窗口输出信息如下： 
                <div> 
                 <div> 
                  <ol> 
                   <li>$ python server.py<br> </li> 
                   <li>Socket created<br> </li> 
                   <li>Socket bind complete<br> </li> 
                   <li>Socket now listening<br> </li> 
                   <li>Connected with 127.0.0.1:60730<br> </li> 
                   <li>Connected with 127.0.0.1:60731</li> 
                  </ol> 
                 </div> 
                 <em>复制代码</em> 
                </div> 线程接管了连接并返回相应数据给客户端。 <br> 这便是我们所要介绍的服务器端编程。 <br> <strong>结论<br> </strong>到这里为止，你已经学习了 Python 的 Socket 基本编程，你可自己动手编写一些例子来强化这些知识。 <br> 你可能会遇见一些问题：Bind failed. Error Code : 98 Message Address already in use，碰见这种问题只需要简单更改服务器端口即可。 <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> </td> 
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