Python3網路學習案例四：編寫Web Proxy

import socket


def handleReq(clientSocket):
    # recv data
    # find the fileName
    # judge if the file named "fileName" if existed
    # if not exists, send req to get it

    recvData = clientSocket.recv(1024).decode()
    fileName = recvData.split()[1].split("//")[1].replace('/', '')
    print("fileName: " + fileName)
    try:
        file = open(fileName, 'rb')
        print("File is found in proxy server.")
        responseMsg = file.readlines()
        for i in range(0, len(responseMsg)):
            clientSocket.sendall(responseMsg[i])
        print("Send, done.")
    except Exception:
        try:
            print("File is not exist.\nSend request to server...")
            proxyClientSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            serverName = fileName.split(":")[0]
            proxyClientSocket.connect((serverName, 80))
            proxyClientSocket.sendall(recvData.encode())
            responseMsg = proxyClientSocket.recv(4069)
            print("File is found in server.")
            proxyClientSocket.sendall(responseMsg)
            print("Send, done.")
            # cache
            cache = open("./" + fileName, 'w')
            cache.writelines(responseMsg.decode().replace('\r\n', '\n'))
            cache.close()
            print("Cache, done.")
        except:
            print("Connect timeout.")


def startProxy(port):
    proxyServerSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    proxyServerSocket.bind(("", port))
    proxyServerSocket.listen(0)
    while True:
        try:
            print("Proxy is waiting for connecting...")
            clientSocket, addr = proxyServerSocket.accept()
            print("Connect established")
            handleReq(clientSocket)
            clientSocket.close()
        except Exception as e:
            print("error: {0}".format(e))
            break
    proxyServerSocket.close()


if __name__ == '__main__':
    while True:
        try:
            port = int(input("choose a port number over 1024:"))
        except ValueError:
            print("Please input an integer rather than {0}".format(type(port)))
            continue
        else:
            if port <= 1024:
                print("Please input an integer greater than 1024")
                continue
            else:
                break
    startProxy(port)