socket加入循环和粘包问题

socket

socket加入通信循环

客户端

import socket

soc = socket.socket()
soc.connect(('127.0.0.1', 8080))

while True:
    inp = input('请输入要发送的信息>>>')
    soc.send(inp.encode('utf-8'))

服务端

import socket

soc = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
soc.bind(('127.0.0.1', 8080))
soc.listen(5)
conn, addr = soc.accept()

while True:
    try:
        data = conn.recv(1024)
        print(data)
    except Exception:
        conn.close()
        break

soc.close()

socket加入连接循环

客户端

import socket

soc = socket.socket()
soc.connect(('127.0.0.1', 8080))

while True:
    inp = input('请输入要发送的消息>>>')
	soc.send(inp.encode('utf-8'))

服务端

import socket

soc = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
soc.bind(('127.0.0.1', 8080))
soc.listen(5)

while True:
    print('等待客户端连接...')
    conn, addr = soc.accept()
    print(f'客户端{addr}已连接上了')
    
    while True:
        try:
            data = conn.recv(1024)
            print(data)
        except Exception:
            break
            
	conn.close()
    
soc.close()

ssh

ssh是远程执行命令

subprocess是执行系统命令的模块

import subprocess

# 执行系统dir命令，把执行的正确结果放到管道中
obj = subprocess.Popen('dir',shell=True,stdout=subprocess.PIPE)
# 拿到正确结果的管道，读出里面的内容
content = obj.stdout.read()
# 因为windows是用gbk编码的，所以要用gbk解码
print(str(content,encoding='gbk'))

粘包问题

粘包现象

客户端

import socket

soc = socket.socket()
soc.connect(('127.0.0.1', 8080))

while True:
    inp = input('请输入要发送的消息>>>')
    soc.send(b'a')
    soc.send(b'b')
    soc.send(b'c')

服务端

import socket

soc = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
soc.bind(('127.0.0.1', 8080))
soc.listen(5)

while True:
    print('等待客户端连接...')
    conn, addr = soc.accept()
    print(f'客户端{addr}已连接上了')
    
    while True:
        try:
            data1 = conn.recv(1024)
            print(data1)
            data2 = conn.recv(1024)
            print(data2)
            data3 = conn,recv(1024)
            print(data3)
        except Exception:
            break
            
	conn.close()
    
soc.close()

客户端发送a、b、c的消息时，服务端有时候会接收到好几个值，而不是单个的a、b、c，这个就是粘包问题。

注意：只有TCP有粘包现象，UDP永远不会粘包

因为TCP协议是基于数据流的，所以收发的消息是不能为空的；但是UDP协议是基于数据报的，即使发送了空内容，UDP协议也会封装上消息头，因此也不会是空内容。

解决粘包问题的方法

给我们要发送的消息加上自定义长度报头，报头中包含我们要发送消息的长度，接收消息的时候，先从读取固定长度的报头，然后再读取真实的长度。

客户端

import json
import socket
import struct

client = socket.socket()
client.connect(('127.0.0.1', 8080))
while True:
    content = input('开始接收信息>>>')
    head_len = struct.unpack('i', client.recv(4))[0]
    dic = json.loads(client.recv(head_len))
    size_len = dic['size']
    name = dic['name']
    count = 0
    data = b''
    with open(name, 'wb') as fw:
        while count < size_len:
            if size_len < 1024:
                data_temp = client.recv(size_len)
            else:
                if size_len - count >= 1024:
                    data_temp = client.recv(1024)
                else:
                    data_temp = client.recv(size_len - count)
                    
			data = data_temp
            count += len(data_temp)
            
		f.write(data)
        
	print('接收完成')
    
client.close()

服务端

import os
import json
import socket
import struct

server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
server.bind(('127.0.0.1', 8080))
server.listen(5)

while True:
    conn, addr = server.accept()
    
    while True:
        dic = {'size': os.path.getsize('run.py'), 'name': 'new_run.py'}
        dic_bytes = bytes(json.dumps(dic), 'utf-8')
        dic_bytes_len = len(dic)
        head = struct.pack('i', dic_bytes_len)
        
        conn.send(head)
        conn.send(dic_bytes)
        with open('run.py', 'rb') as fr:
            for line in fr:
                conn.send(line)
                
	conn.close()
    
server.close()