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\r\n\r\n" 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\n') #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 if __name__ == "__main__": CONNECTION_LIST = [] #list of socket clients server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) #Add server socket to the list of readable connections print "Chat server started on port " + str(PORT) while 1: for sock in read_sockets: 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() poll = select.poll() while True: |
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》