python学习笔记(47)黏包现象

本质原因：不知道要接收多大的数据

tcp会黏包但是不会丢包　　#因为组合(发送端缓冲区(tcp特有)满)和拆分(多个包接收)数据包

udp不会黏包，但是会丢包　　#sendto函数最大能发送数据的长度为：65535-ip头(20)-UDP头(8)=65507字节

　　　　　　　　　　　　　　超长会报错并丢包

tcp_sever:

import socket
sk = socket.socket()
sk.bind(('127.0.0.1',8090))
sk.listen()

conn, addr = sk.accept()
while True:
    cmd = input('>>>')
    conn.send(cmd.encode('gbk'))
    ret = conn.recv(1024).decode('utf-8')
    print(ret)

conn.close()
sk.close()

tcp_client:

import socket
import subprocess
sk = socket.socket()
sk.connect(('127.0.0.1',8090))
while 1:
    cmd = sk.recv(1024).decode('gbk')
    ret = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    std_out = 'stdout:' + (ret.stdout.read().decode('gbk'))
    std_err = 'stderr:' + (ret.stderr.read().decode('gbk'))
    sk.send(std_out.encode('utf-8'))
    sk.send(std_err.encode('utf-8'))
sk.close()

udp_sever:

import socket
sk = socket.socket(type=socket.SOCK_DGRAM)
sk.bind(('127.0.0.1',8090))
msg,addr = sk.recvfrom(1024)
while True:
    cmd = input('>>>')
    if cmd == 'q':
        break
    sk.sendto(cmd.encode('gbk'),addr)
    ret = sk.recv(1024).decode('utf-8')
    print(ret)

sk.close()

udp_client:

import socket
import subprocess
sk = socket.socket(type=socket.SOCK_DGRAM)
addr = ('127.0.0.1',8090)
while 1:
    sk.sendto('吃了么'.encode('utf-8'),addr)
    cmd,addr = sk.recvfrom(1024)
    ret = subprocess.Popen(cmd.decode('gbk'), shell=True,
                           stdout=subprocess.PIPE,
                           stderr=subprocess.PIPE)
    std_out = 'stdout:' + (ret.stdout.read().decode('gbk'))
    std_err = 'stderr:' + (ret.stderr.read().decode('gbk'))
    sk.sendto(std_out.encode('utf-8'),addr)
    sk.sendto(std_err.encode('utf-8'),addr)
sk.close()