网络编程中的TCP和UDP

from socket import *


tcp_server = socket(AF_INET, SOCK_STREAM)

# 绑定本地信息，TCP服务器程序监听所有网络接口上的88888端口
host_port = ('', 88888)  
tcp_server.bind(host_port)

# 使用socket创建的套接字默认的属性是主动的，使用listen将其变为被动的，这样就可以接收别人的链接了
tcp_server.listen(5)

while True:


    newSocket, host_port = tcp_server.accept()

    while True:

        # 最大接收1024个字节
        recvData = newSocket.recv(1024)

        if len(recvData) > 0:
            print('recv:', recvData)
        else:
            break

        sendData = input("send:")
        newSocket.send(sendData.encode('utf8'))


    newSocket.close()

tcp_server.close()

from socket import *


tcp_client = socket(AF_INET, SOCK_STREAM)

# 链接服务器
host_port = ('127.0.0.1', 88888)
tcp_client.connect(host_port)

while True:


    sendData = input("send：")

    if len(sendData) > 0:
        tcp_client.send(sendData.encode('utf8'))
    else:
        break

    # 最大接收1024个字节
    recvData = tcp_client.recv(1024)
    print('recv:', recvData.decode('uft8'))

tcp_client.close()

import socket

sk = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
# 绑定 IP 和端口号
sk.bind(('127.0.0.1', 88888))
while True:

  msg, addr = sk.recvfrom(1024)

  print('来自[%s:%s]的消息: %s' % (addr[0], addr[1], msg.decode('utf-8')))
 

  inp = input('>>>')

  sk.sendto(inp.encode('utf-8'), addr)
 
sk.close()

import socket
 

sk = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
addr = ('127.0.0.1', 88888)
while True:

  msg = input('>>>')
  sk.sendto(msg.encode('utf-8'), addr)
  msg_recv, addr = sk.recvfrom(1024)
  print(msg_recv.decode('utf-8'))
 
sk.close()

import socket  
import struct  
  
def handle_client(sock, filename):  
    # 假设文件存在且小于65535字节  
    try:  
        with open(filename, 'rb') as file:  
            data = file.read(512)  # TFTP块大小为512字节  
            block_number = 1  
            while data:  
                # 发送DATA包：block_number + data  
                block_info = struct.pack('!H', block_number)  # 网络字节序的短整型  
                sock.sendto(block_info + data, client_address)  
                  
                # 等待ACK  
                ack_data, _ = sock.recvfrom(2)  # 只接收block number  
                ack_block_number = struct.unpack('!H', ack_data)[0]  
                  
                if ack_block_number != block_number:  
                    print("Incorrect block number in ACK")  
                    break  
                  
                block_number += 1  
                data = file.read(512)  
    except FileNotFoundError:  
        # 发送ERROR包  
        error_code = 1  # File not found  
        error_msg = struct.pack('!HH', error_code, 0)  # TFTP错误消息格式  
        sock.sendto(error_msg, client_address)  
  
def start_tftp_server(port, root_dir):  
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  
    server_socket.bind(('0.0.0.0', port))  
  
    print(f"TFTP server listening on port {port}...")  
  
    while True:  
        data, client_address = server_socket.recvfrom(1024)  # 接收RRQ或WRQ请求  
        # 这里简化处理，只处理RRQ  
        if data.startswith(b'\x00\x01'):  # RRQ的opcode  
            filename = data[2:].decode().split(b'\x00')[0]  
            filepath = f"{root_dir}/{filename}"  
            handle_client(server_socket, filepath)  
  
if __name__ == "__main__":  
    start_tftp_server(69, './files') 

import socket  
import struct  
  
def request_file(server_ip, server_port, filename):  
    client_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  
  
    # 发送RRQ请求  
    rrq = b'\x00\x01' + filename.encode() + b'\x00' + b'octet' + b'\x00'  # mode为octet  
    client_socket.sendto(rrq, (server_ip, server_port))  
  
    block_number = 0  
    data = b''  
  
    while True:  
        # 接收DATA包  
        data_packet, _ = client_socket.recvfrom(514)  # 512字节数据 + 2字节块号  
        block_number = struct.unpack('!H', data_packet[:2])[0]  
        if block_number == 0:  # 假设块号为0表示文件结束或错误  
            break  
  
        data += data_packet[2:]  
  
        # 发送ACK  
        ack = struct.pack('!H', block_number)  
        client_socket.sendto(ack, (server_ip, server_port))  
  
    client_socket.close()  
  
    # 处理接收到的数据（例如，写入文件）  
    with open(filename, 'wb') as file:  
        file.write(data)  
  
if __name__ == "__main__":  
    request_file('127.0.0.1', 69)
    file_name = 'example.txt'  
    request_file(server_addr, 69, file_name)