Python基础复习（第四天）

网络编程

OSI七层协议

  应，表，会，传，网，数，物

socket编程

  1.Socket是应用层与TCP/IP协议族通信的中间软件抽象层，它是一组接口

socket模块用法

  Ⅰ. TCP服务端
  s = socket(socket.AF_INET,socket.SOCKET_STREAM)
  s.bind(("127.0.0.1",8080))
  s.listen(5)
  conn,addr = s.accept()
  conn.recv(1024)
  conn.send()
  conn.close()
  s.close()

  Ⅱ. TCP客户端
  c = socket(socket.AF_INET,socket.SOCK_STREAM)
  c.connect(("127.0.0.1",8080))
  c.send("".encode("utf8")) # 只能发送字节类型
  c.recv(1024)
  c.close()

链接循环和通信循环

  1. TCP客户端
  s = socket(socket.AF_INET,socket.SOCKET_STREAM)
  s.bind(("127.0.0.1",8080)
  s.listen(5)
  while True: # 链接循环
        conn,addr = s.accept(5) 
        while True:  # 通信循环                        
              conn.recv(1024)
              conn.send("".encode("utf8"))
        conn.close()
  s.close()
  
  2. TCP服务端
  c = socket(socket.AF_INET,socket.SOCKET_STREAM)
  c.connect(("127.0.0.1",8080))

  while True:
       msg = input(">>:").strip()
       if len(msg) == 0: continue
       c.send(msg.encode("utf8"))

       c.recv(1024)
        
  c.close()

UDP服务端

  s = socket(socket.AF_INET,socket.SOCK_DGRAM)
  s.bind(("127.0.0.1",8080))
  while True:
        msg,addr = s.recvfrom(1024)
        s.sendto(msg.upper(),addr)

UDP客户端

  c = socket(socket.AF_INET,socket.SOCK_DGRAM)
  while True:
        msg = input(">>:").strip()
        if msg == 0: continue
        c.sendto(msg.encode("utf8"),("127.0.0.1",8080))
        back_msg,addr = c.recvfrom(1024)

粘包现象

  1. TCP流式协议才会出现粘包现象
  2. 如何解决粘包问题（这里用到一个模块，struct，可以把一个类型转成固定长度的bytes，并且可以反解）
        import json,struct
        header = {'file_size':1000000000,'file_name':'/d/movie/jap/youkonw.txt','md5':"5451254121"}
        head_bytes = bytes(json.dumps(header),encoding='utf8')          
        head_len_bytes = struct.pack('i',len(head_bytes))
        c.send(head_len_bytes)
        c.send(head_bytes)
        c.sendall()

        import json,struct
        head_len_bytes = conn.recv(4)
        x = struct('i',head_len_bytes)[0]
        head_bytes = conn.recv(x)
        header = json.loads(head_bytes)
        
        real_data_len = head["file_size"]
        conn.recv(read_data_len)