1. TCP协议下的如何解决粘包问题

　　TCP(transport control protocol 传输控制协议)  使用Nagle算法，将多次间隔较小且数据量小的数据，合并成大的数据块；接受端无法识别每条数据的边界，因此产生粘包现象。

"""
Server
"""
from socket import *

back_log = 5
bufsize = 1024
ip_port = ('127.0.0.1', 8080)

tcp_server = socket(AF_INET, SOCK_STREAM) # 数据流
tcp_server.bind(ip_port)
tcp_server.listen(back_log)

while True:
print('服务端开始处理连接。。。')
conn, addr = tcp_server.accept()
print('客户端连接', conn)
print('客户端地址', addr)
while True:
try:
data = conn.recv(bufsize)
if not data:
break
print('接收到的数据', data)
conn.send(data.upper())
except Exception as e:
print(e)
break

"""
Client
"""
from socket import *

bufsize = 1024
ip_port = ('127.0.0.1', 8080)

tcp_client = socket(AF_INET, SOCK_STREAM)
tcp_client.connect(ip_port)
tcp_client.send('hello'.encode('utf-8'))
tcp_client.send('world'.encode('utf-8'))
response = tcp_client.recv(bufsize)
print('response is ==> ', response) # response is ==> b'HELLOWORLD'

解决思路：告知接收端数据长度，导入struct模块，将字节长度封装成4个字节发送给接收方；

服务端 =====》TCP实现远程操作命令

from socket import *
import subprocess,struct

bufsize = 1024
back_log = 5
ip_port = ('127.0.0.1', 8080)

tcp_server = socket(AF_INET, SOCK_STREAM)
tcp_server.bind(ip_port)
tcp_server.listen(back_log)
while True:
conn, addr = tcp_server.accept()
print('current connection', conn)
while True:
try:
cmd = conn.recv(bufsize)
if not cmd:
break
print('data from client', cmd)

        res = subprocess.Popen(cmd.decode('utf-8'), shell=True,  
                               stderr=subprocess.PIPE,  
                               stdin=subprocess.PIPE,  
                               stdout=subprocess.PIPE)  
        cmd\_res = res.stderr.read()  
        if not cmd\_res:  
            cmd\_res = res.stdout.read()  
        print('response is:', cmd\_res)

        data\_length = struct.pack('i', len(cmd\_res))  
        conn.send(data\_length)  
        conn.send(cmd\_res)  
    except Exception as e:  
        print(e)  
        break  
# conn.close()

客户端 ====》

from socket import *
import struct

bufsize = 100
ip_port = ('127.0.0.1', 8080)
tcp_client = socket(AF_INET, SOCK_STREAM)
tcp_client.connect(ip_port)

while True:
cmd = input('>>>> ').strip()
if not cmd:
continue
if cmd == 'quit':
break
tcp_client.send(cmd.encode('utf-8'))

length\_data = tcp\_client.recv(4)

length = struct.unpack('i', length\_data)\[0\]  
print(length)  
response = b''  
recsize = 0  
while recsize < length:  
    response += tcp\_client.recv(bufsize)  
    recsize = len(response)  
    # print('execute result is:', response)  # 接受字节长度小于发送数据长度，产生粘包  
print('execute result is:', response.decode('gbk'))  

tcp_client.close()

2. TCP协议如何实现多个客户端连接(并发处理)

导入socketserver模块，实现ocketserver.BaseRequestHandler，重写 handle 方法

使用

ThreadingTCPServer，线程实现并发

import socketserver

class MyServer(socketserver.BaseRequestHandler):
def handle(self): print('conn is', self.request) # conn
print('addr is', self.client_address) # addr

    while True:  
        try:  
            data = self.request.recv(1024)  
            if not data:  
                break  
            self.request.sendall(data.upper())  
        except Exception as e:  
            print(e)  
            break

if __name__ == '__main__':
ip_port = ('127.0.0.1', 8080)
s = socketserver.ThreadingTCPServer(ip_port, MyServer)
s.serve_forever()

3. 基于UDP套接字

　　UDP 与TCP 不同，使用socket时用的时 SOCK_DGRAM 数据报

　　sendto()发送的是元组数据类型，包含数据以及连接

　　recvfrom()接收的也是数据以及连接

服务端 ====》

from socket import *

ip_port = ('127.0.0.1', 8080)
buf_size = 1024

udp_server = socket(AF_INET, SOCK_DGRAM) # datagram 数据报
udp_server.bind(ip_port)

while True:
data, addr = udp_server.recvfrom(buf_size)
print(data)
udp_server.sendto(data.upper(), addr)

客户端====》

from socket import *

ip_port = ('127.0.0.1', 8080)
buf_size = 1024

udp_client = socket(AF_INET, SOCK_DGRAM) # datagram 数据报

while True:
msg = input('==>: ').strip()
udp_client.sendto(msg.encode('utf-8'), ip_port)
response, addr = udp_client.recvfrom(buf_size)
print(response.decode('utf-8'))