计算机网络：自顶向下方法读书笔记（五）

编程练习1：Web服务器

from socket import *
import sys  # 系统库

serverSocket = socket(AF_INET, SOCK_STREAM)

serverSocket.bind(('', 8088))
serverSocket.listen(1)
print('The server is ready to receive')
while True:
    # Establish the connection
    print('Ready to serve...')
    connectionSocket, addr = serverSocket.accept()
    try:
        message = connectionSocket.recv(1024).decode()
        filename = message.split()[1]
        # 打开服务器所在目录下的对应文件
        f = open(filename[1:])
        outputdata = f.read()
        # Send one HTTP header line into socket
        # 必须写状态行，否则浏览器无法响应
        connectionSocket.send("HTTP/1.1 200 OK\r\n\r\n".encode())
        # Send the content of the requested file to the client
        for i in range(0, len(outputdata)):
            connectionSocket.send(outputdata[i].encode())
        connectionSocket.send("\r\n".encode())
        connectionSocket.close()
    except IOError:
        # Send response message for file not found
        # 如果返回这个状态码，则页面会根据404状态码显示页面
        connectionSocket.send("HTTP/1.1 404 Not Found\r\n\r\n".encode())
        # 如果按下面的内容返回，则请求成功页面，页面写着404 NOT Found
        # connectionSocket.send("HTTP/1.1 200 OK\r\n\r\n".encode())
        # connectionSocket.send("404 Not Found".encode())
        # Close client socket
        connectionSocket.close()
    serverSocket.close()
    sys.exit() #结束进程用

编程练习2：UDP ping 程序

• server

# 随机库
import random
from socket import *
serverSocket = socket(AF_INET, SOCK_DGRAM)
serverSocket.bind(('', 12000))
while True:
    rand = random.randint(0, 10)
    message, address = serverSocket.recvfrom(1024)
    modifiedMessage = message.upper()
    if rand < 4:
        continue
    serverSocket.sendto(modifiedMessage, address)

• client

from socket import *
import time

serverName = '127.0.0.1'
serverPort = 12000
clientSocket = socket(AF_INET, SOCK_DGRAM)
clientSocket.settimeout(1)
for i in range(10):
    start = time.time()
    try:
        clientSocket.sendto('message'.encode(), (serverName, serverPort))
        modifiedMessage, serverAddress = clientSocket.recvfrom(1024)
        end = time.time()
        print('Ping', i, end - start)
    except:
        print('Request timed out')
clientSocket.close()

编程练习3：邮件客户

from socket import *
title = "Subject: Hello!"
msg = "\n\n I love computer networks!"
endmsg = "\r\n.\r\n"
mailserver = 'smtp.163.com'  # Fill in start #Fill in end
clientSocket = socket(AF_INET, SOCK_STREAM)
# 连接邮件服务器
clientSocket.connect((mailserver, 25))
recv = clientSocket.recv(1024).decode()
print(recv)
if recv[:3] != '220':
    print('220 reply not received from server.')
# 向服务器标识用户身份
heloCommand = 'HELO smtp.163.com\r\n'
clientSocket.send(heloCommand.encode())
recv1 = clientSocket.recv(1024).decode()
print(recv1)
if recv1[:3] != '250':
    print('250 reply not received from server.')
# 登录指令
loginCommand = 'AUTH LOGIN\r\n'
clientSocket.send(loginCommand.encode())
recv2 = clientSocket.recv(1024).decode()
print(recv2)
# 输入登录名和密码，需要使用base64编码
clientSocket.send('xxx\r\n'.encode())
recv3 = clientSocket.recv(1024).decode()
print(recv3)
clientSocket.send('xxx\r\n'.encode())
recv4 = clientSocket.recv(1024).decode()
print(recv4)
# 发送者邮箱
mailCommand = 'MAIL FROM: <[email protected]>\r\n'
clientSocket.send(mailCommand.encode())
recv5 = clientSocket.recv(1024).decode()
print(recv5)
if recv5[:3] != '250':
    print('250 reply not received from server.')
# 接收者邮箱
rcptCommand = 'RCPT TO: <[email protected]>\r\n'
clientSocket.send(rcptCommand.encode())
recv6 = clientSocket.recv(1024).decode()
print(recv6)
if recv6[:3] != '250':
    print('250 reply not received from server.')
# 输入信息指令
clientSocket.send(('DATA\r\n').encode())
recv7 = clientSocket.recv(1024).decode()
print(recv7)
# 输入信息内容并结束、发送（注意会被当做垃圾邮件处理，我这里测试只是自己发给自己）
clientSocket.send((title+msg+endmsg).encode())
recv8 = clientSocket.recv(1024).decode()
print(recv8)
if recv8[:3] != '250':
    print('250 reply not received from server.')
# 结束指令
clientSocket.send('QUIT\r\n'.encode())
recv9 = clientSocket.recv(1024).decode()
print(recv9)

编程练习4：多线程web代理服务器

from socket import *
import sys
if len(sys.argv) <= 1:
    print('Usage : "python ProxyServer.py server_ip"\n[server_ip : It is the IP Address Of Proxy Server]')
    sys.exit(2)
tcpSerSock = socket(AF_INET, SOCK_STREAM)
tcpSerSock.bind((sys.argv[1], 8080))
tcpSerSock.listen(10)
while 1:
    print('Ready to serve...')
    tcpCliSock, addr = tcpSerSock.accept()
    print('Received a connection from:', addr)
    message = tcpCliSock.recv(4096)
    print(message)
    print(message.split()[1])
    filename = message.split()[1].partition('/'.encode())[2]
    print(filename)
    fileExist = "false"
    filetouse = "/" + filename.decode()
    print(filetouse)
    try:
        f = open(filetouse[1:], "r")
        outputdata = f.read()
        fileExist = "true"
        tcpCliSock.send("HTTP/1.1 200 OK\r\n".encode())
        tcpCliSock.send("Content-Type:text/html\r\n".encode())
        for i in range(0, len(outputdata)):
            tcpCliSock.send(outputdata[i].encode())
        tcpCliSock.send("\r\n".encode())
        tcpCliSock.close()
        print('Read from cache')e
    except IOError:
        if fileExist == "false":
            c = socket(AF_INET, SOCK_STREAM)
            hostn = filename.replace("www.".encode(), "".encode(), 1)
            print(hostn)
            try:
                hostnaddr = gethostbyname(hostn.decode())
                print(hostnaddr)
                c.connect((hostnaddr, 80))
                c.send(("GET /" + " HTTP/1.1\r\n" + "Host:" + filename.decode() + "\r\n\r\n").encode())
                response = c.recv(4096)
                tmpFile = open("./" + filename.decode(), "wb")
                tmpFile.write(response)
                tmpFile.close()
            except:
                print(error)
                print("Illegal request")
        else:
            tcpCliSock.send("HTTP/1.1 200 OK\r\n".encode())
            tcpCliSock.send("404 Not Found".encode())
    tcpCliSock.close()