Python_NAT

sockMiddle_server.py

 import sys
 import socket
 import threading

 #回复消息，原样返回
 def replyMessage(conn):
     while True:
         data = conn.recv(1024)
         conn.send(data)
         if data.decode().lower() == 'bye':
             break
     conn.close()

 def main():
     sockScr = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     sockScr.bind(('', port))
     sockScr.listen(200)
     while True:
         try:
             conn, addr = sockScr.accept()
             #只允许特定主机访问本服务器
             if addr[0] != onlyYou:
                 conn.close()
                 continue
             #创建并启动线程
             t = threading.Thread(target=replyMessage, args=(conn,))
             t.start()
         except:
             print('error')

 if __name__ == '__main__':
     try:
         #获取命令行参数
         port = int(sys.argv[1])
         onlyYou = sys.argv[2]
         main()
     except:
         print('Must give me a number as port')
         

sockMiddle.py

 import sys
 import socket
 import threading

 def middle(conn, addr):
     #面向服务器的Socket
     sockDst = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     sockDst.connect((ipServer,portServer))
     while True:
         data = conn.recv(1024).decode()
         print('收到客户端消息：'+data)
         if data == '不要发给服务器':
             conn.send('该消息已被代理服务器过滤'.encode())
             print('该消息已过滤')
         elif data.lower() == 'bye':
             print(str(addr)+'客户端关闭连接')
             break
         else:
             sockDst.send(data.encode())
             print('已转发服务器')
             data_fromServer = sockDst.recv(1024).decode()
             print('收到服务器回复的消息：'+data_fromServer)
             if data_fromServer == '不要发给客户端':
                 conn.send('该消息已被代理服务器修改'.encode())
                 print('消息已被篡改')
             else:
                 conn.send(b'Server reply:'+data_fromServer.encode())
                 print('已转发服务器消息给客户端')

     conn.close()
     sockDst.close()

 def main():
     sockScr = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     sockScr.bind(('', portScr))
     sockScr.listen(200)
     print('代理已启动')
     while True:
         try:
             conn, addr = sockScr.accept()
             t = threading.Thread(target=middle, args=(conn, addr))
             t.start()
             print('新客户：'+str(addr))
         except:
             pass

 if __name__ == '__main__':
     try:
         #(本机IP地址,portScr)<==>(ipServer,portServer)
         #代理服务器监听端口
         portScr = int(sys.argv[1])
         #服务器IP地址与端口号
         ipServer = sys.argv[2]
         portServer = int(sys.argv[3])
         main()
     except:
         print('Sth error')

sockMiddle_client.py

 import sys
 import socket
 import threading

 def middle(conn, addr):
     #面向服务器的Socket
     sockDst = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     sockDst.connect((ipServer,portServer))
     while True:
         data = conn.recv(1024).decode()
         print('收到客户端消息：'+data)
         if data == '不要发给服务器':
             conn.send('该消息已被代理服务器过滤'.encode())
             print('该消息已过滤')
         elif data.lower() == 'bye':
             print(str(addr)+'客户端关闭连接')
             break
         else:
             sockDst.send(data.encode())
             print('已转发服务器')
             data_fromServer = sockDst.recv(1024).decode()
             print('收到服务器回复的消息：'+data_fromServer)
             if data_fromServer == '不要发给客户端':
                 conn.send('该消息已被代理服务器修改'.encode())
                 print('消息已被篡改')
             else:
                 conn.send(b'Server reply:'+data_fromServer.encode())
                 print('已转发服务器消息给客户端')

     conn.close()
     sockDst.close()

 def main():
     sockScr = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     sockScr.bind(('', portScr))
     sockScr.listen(200)
     print('代理已启动')
     while True:
         try:
             conn, addr = sockScr.accept()
             t = threading.Thread(target=middle, args=(conn, addr))
             t.start()
             print('新客户：'+str(addr))
         except:
             pass

 if __name__ == '__main__':
     try:
         #(本机IP地址,portScr)<==>(ipServer,portServer)
         #代理服务器监听端口
         portScr = int(sys.argv[1])
         #服务器IP地址与端口号
         ipServer = sys.argv[2]
         portServer = int(sys.argv[3])
         main()
     except:
         print('Sth error')

'''
启动3个终端cd到文件目录后:各终端执行一条语句
python sockMiddle_server.py 10000 10.2.1.2
python sockMiddle.py 30800 10.2.1.2 10000
python sockMiddle_client.py 10.2.1.2 30800
'''