关于网络编程以及socket 等一些概念和函数介绍就不再重复了，这里示例性用python 编写客户端和服务器端。
一、最简单的客户端流程：
1. Create a socket
2. Connect to remote server
3. Send some data
4. Receive a reply
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#Socket client example in python
import socket #for sockets import sys #for exit import struct import time #create an INET, STREAMing socket try: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) except socket.error: print 'Failed to create socket' sys.exit() print 'Socket Created' host = 'www.google.com'; port = 80; try: remote_ip = socket.gethostbyname( host ) except socket.gaierror: #could not resolve print 'Hostname could not be resolved. Exiting' sys.exit() #Connect to remote server s.connect((remote_ip , port)) print 'Socket Connected to ' + host + ' on ip ' + remote_ip #Send some data to remote server message = "GET / HTTP/1.1 " try : #Set the whole string s.sendall(message) except socket.error: #Send failed print 'Send failed' sys.exit() print 'Message send successfully' def recv_timeout(the_socket,timeout= 2): #make socket non blocking the_socket.setblocking( 0) #total data partwise in an array total_data=[]; data= ''; #beginning time begin=time.time() while 1: #if you got some data, then break after timeout if total_data and time.time()-begin > timeout: break #if you got no data at all, wait a little longer, twice the timeout elif time.time()-begin > timeout* 2: break #recv something try: data = the_socket.recv( 8192) if data: total_data. append(data) #change the beginning time for measurement begin=time.time() else: #sleep for sometime to indicate a gap time.sleep( 0. 1) except: pass #join all parts to make final string return ''. join(total_data) #get reply and print print recv_timeout(s) #Close the socket s. close() |
需要注意的是也许http 响应数据比较大，要经过多次才能完整接收，设置socket 非阻塞，设定timeout，最后join 数据；因为我们并不知道具体数据到底多大，故不能这样使用 data. s.recv(4096 , socket.MSG_WAITALL); 如果最后一次来的数据不够4096，那么将一直阻塞。输出如下：
二、最简单的服务器端流程：
1. Open a socket
2. Bind to a address(and port).
3. Listen for incoming connections.
4. Accept connections
5. Read/Send
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import socket
import sys HOST = '' # Symbolic name meaning all available interfaces PORT = 8888 # Arbitrary non-privileged port s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) print 'Socket created' try: s.bind((HOST, PORT)) except socket.error , msg: print 'Bind failed. Error Code : ' + str(msg[ 0]) + ' Message ' + msg[ 1] sys.exit() print 'Socket bind complete' s.listen( 10) print 'Socket now listening' #now keep talking with the client while 1: #wait to accept a connection - blocking call conn, addr = s.accept() print 'Connected with ' + addr[ 0] + ':' + str(addr[ 1]) data = conn.recv( 1024) reply = 'OK...' + data if not data: break conn.sendall(reply) conn. close() s. close() |
三、上述程序的缺点是每个连接上来就回应一次就不再搭理了，显然不可取，用多线程改进如下：
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import socket
import sys from thread import * HOST = '' # Symbolic name meaning all available interfaces PORT = 8888 # Arbitrary non-privileged port s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) print 'Socket created' #Bind socket to local host and port try: s.bind((HOST, PORT)) except socket.error , msg: print 'Bind failed. Error Code : ' + str(msg[ 0]) + ' Message ' + msg[ 1] sys.exit() print 'Socket bind complete' #Start listening on socket s.listen( 10) print 'Socket now listening' #Function for handling connections. This will be used to create threads def clientthread(conn): #Sending message to connected client conn.send( 'Welcome to the server. Type something and hit enter ') #send only takes string #infinite loop so that function do not terminate and thread do not end. while True: #Receiving from client data = conn.recv( 1024) reply = 'OK...' + data if not data: break conn.sendall(reply) #came out of loop conn. close() #now keep talking with the client while 1: #wait to accept a connection - blocking call conn, addr = s.accept() print 'Connected with ' + addr[ 0] + ':' + str(addr[ 1]) #start new thread takes 1st argument as a function name to be run, second is the tuple of arguments to the function. start_new_thread(clientthread ,(conn,)) s. close() |
即每accept 返回一个连接，就创建一个线程对其服务。
启动server，然后开两个窗口telnet 上去，如下：
四、接下来，我们再用select 来实现，函数原型如下：
read_sockets,write_sockets,error_sockets = select(read_fds , write_fds, except_fds [, timeout]);
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#Socket server in python using select function
import socket, select #Function to broadcast chat messages to all connected clients def broadcast_data(sock, message): #Do not send the message to master socket and the client who has send us the message for socket in CONNECTION_LIST: if socket != server_socket and socket != sock: try: socket.send(message) except: #broken socket connection may be, chat client pressed ctrl+c for example socket. close() CONNECTION_LIST. remove(socket) if __name__ == "__main__": CONNECTION_LIST = [] #list of socket clients RECV_BUFFER = 4096 #Advisable to keep it as an exponent of 2 PORT = 5000 server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) #this has no effect, why? server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) server_socket.bind(( "0.0.0.0", PORT)) server_socket.listen( 10) #Add server socket to the list of readable connections CONNECTION_LIST. append(server_socket) print "Chat server started on port " + str(PORT) while 1: #Get the list sockets which are ready to be read through select read_sockets, write_sockets, error_sockets = select.select(CONNECTION_LIST, [], []) for sock in read_sockets: #New connection if sock == server_socket: #handle the case in which there is a new connection recieved through server_socket sockfd, addr = server_socket.accept() CONNECTION_LIST. append(sockfd) print "Client (%s, %s) connected" % addr #Some incoming message from a client else: #Data recieved from client, process it try: #In windows, sometimes when a Tcp program closes abruptly #a "Connection reset by peer" exception will be thrown data = sock.recv(RECV_BUFFER) #echo back the client message if data: sock.send( 'Ok...' + data) #client disconnected, so remove from socket list except: broadcast_data(sock, "Client (%s, %s) is offline" % addr) print "Client (%s, %s) is offline" % addr sock. close() CONNECTION_LIST. remove(sock) continue server_socket. close() |
五、最后使用poll 来实现，如下：
launcelot.py
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#!/usr/bin/env python
#coding=utf-8 #Constants and routines for supporting a certain network conversation. import sys, socket PORT = 1060 qa = (( 'What is your name?', 'My name is Sir Launcelot of Camelot.'), ( 'What is your quest?', 'To seek the Holy Grail.'), ( 'What is your favorite color?', 'Blue.')) qadict = dict(qa) def recv_until(sock, suffix): message = '' while not message. endswith(suffix): data = sock.recv( 4096) if not data: raise EOFError( 'socket closed before we saw %r' % suffix) message += data return message def setup(): if len(sys.argv) != 2: print >>sys.stderr, 'usage: %s interface' % sys.argv[ 0] exit( 2) interface = sys.argv[ 1] sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) sock.bind((interface, PORT)) sock.listen( 128) print 'Ready and listening at %r port %d' % (interface, PORT) return sock |
poll_server.py
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# An event-driven approach to serving several clients with poll().
import launcelot import select listen_sock = launcelot.setup() sockets = {listen_sock. fileno():listen_sock} requests = {} responses = {} poll = select.poll() poll.register(listen_sock, select.POLLIN) while True: for fd, event in poll.poll(): sock = sockets[fd] #Removed closed sockets from our list. if event & (select.POLLHUP | select.POLLERR | select.POLLNVAL): poll.unregister(fd) del sockets[fd] requests. pop(sock, None) responses. pop(sock, None) #Accept connections from new sockets. elif sock is listen_sock: newsock, sockname = sock.accept() newsock.setblocking( False) fd = newsock. fileno() sockets[fd] = newsock poll.register(fd, select.POLLIN) requests[newsock] = '' #Collect incoming data until it forms a question. elif event & select.POLLIN: data = sock.recv( 4096) if not data: #end of file sock. close() # make POLLNVAL happen next time continue requests[sock] += data. replace( ' ', '') if '?' in requests[sock]: question = requests. pop(sock) answer = dict(launcelot.qa)[question] poll.modify(sock, select.POLLOUT) responses[sock] = answer #Send out pieces of each reply until they are all sent elif event & select.POLLOUT: response = responses. pop(sock) n = sock.send(response) if n < len(response): responses[sock] = response[n:] else: poll.modify(sock, select.POLLIN) requests[sock] = '' |
客户端需要发送launcelot.qa 其中一个问题，然后server 索引到答案发回给客户端。
参考：
《Foundations of Python Network Programming》