python day31--网络编程,tcp,udp的指令，及黏包

一、TCP

tcp中遇到黏包会让数据传输完。

server

import socket
sk=socket.socket()
sk.bind(('127.0.0.1',8090))
sk.listen()
while True:
    cmd=input('>>>')
    conn,addr=sk.accept()
    conn.send(cmd.encode('utf-8'))
    ret=conn.recv(1024).decode('utf-8')
    print(ret) 
conn.close()
sk.close()

client

import socket
import subprocess
sk=socket.socket()
sk.connect(('127.0.0.1',8090))
while True:
    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')
    print(std_err)
    print(std_out)
    sk.send(std_out.encode('utf-8'))
    sk.send(std_err.encode('utf-8'))
sk.close()

二、UDP

udp传输遇不会黏包。

server

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('utf-8'),addr)
    msg,addr=sk.recvfrom(1024)
    print(msg.decode('utf-8'))

sk.close()

client

import  socket
import  subprocess
sk=socket.socket(type=socket.SOCK_DGRAM)
addr=('127.0.0.1',8090)

sk.sendto('吃了吗'.encode('utf-8'),addr)
while True:
        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')
        print(std_err)
        print(std_out)
        sk.sendto(std_out.encode('utf-8'),addr)
        sk.sendto(std_err.encode('utf-8'),addr)
sk.close()

三、黏包

tcp协议的拆包机制：网络设备在传输时会把数据拆成几块来传输，这样会产生数据碎片，从而造成数据丢失。

tcp黏包：发送方引起的粘包是由TCP协议本身造成的，TCP为提高传输效率，发送方往往要收集到足够多的数据后才发送一个TCP段。若连续几次需要send的数据都很少，通常TCP会根据优化算法把这些数据合成一个TCP段后一次发送出去，这样接收方就收到了粘包数据。

四、网盘作业

server

import socket
sk=socket.socket()
sk.bind(('127.0.0.1',8080))
sk.listen()
conn,addr=sk.accept()
user=conn.recv(1024).decode('utf-8')
pwd=conn.recv(1024).decode('utf-8')
print(user,pwd)
while True:
    if user=='alex' and pwd=='123456':
        conn.send(bytes('1.上传文件  2.下载文件',encoding='utf-8'))
        shell=conn.recv(10240).decode('utf-8')
        print(shell)
        if shell== '1':
            txt=conn.recv(10240).decode('utf-8')
            with open('a.txt','w',encoding='utf-8') as f1:
                f1.write(txt)
                conn.send(bytes('上传成功',encoding='utf-8'))
                break
        elif shell== '2':
            with open('b.txt','r',encoding='utf-8') as f1:
                conn.send(bytes(f1.read(), encoding='utf-8'))
                conn.send(bytes('下载成功',encoding='utf-8'))
                break
conn.close()
sk.close()

client

import socket
sk=socket.socket()
sk.connect(('127.0.0.1',8080))
user=input('输入用户名：')
pwd=input('输入密码：')
sk.send(bytes(user,encoding='utf-8'))
sk.send(bytes(pwd,encoding='utf-8'))
shell=sk.recv(1024).decode('utf-8')
print(shell)
cmd=input('>>>')
sk.send(bytes(cmd,encoding='utf-8'))
while True:
    if cmd=='1':
        with open('a1.txt','r',encoding='utf-8') as f1:
            sk.send(bytes(f1.read(),encoding='utf-8'))
            msg=sk.recv(10240).decode('utf-8')
            print(msg)
            break
    elif cmd=='2':
        with open('C:/Users/lenovo/Desktop/111/b1.txt','w',encoding='utf-8') as f1:
            info=sk.recv(10240).decode('utf-8')
            msg=sk.recv(10240).decode('utf-8')
            f1.write(info)
            print(msg)
            break
sk.close()