文件传输完成后发送消息

Question

我是套接字编程的新手。我正在尝试将4个文件从一台主机发送到另一台主机。这是代码：

发件人：

from __future__ import print_function
import socket
from struct import pack

HOST = '10.0.0.2'
PORT = 12345
BUFSIZE = 4096

def send(sock, data):
    while data:
        sent = sock.send(data)
        data = data[sent:]

def send_file(fname):
    with open(fname, 'rb') as f:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            sock.connect((HOST, PORT))
        except socket.error as err:
            print(err, HOST, PORT)
            sock.close()
            return

        # Send the file name length & the filename itself in one packet          
        send(sock, pack('B', len(fname)) + fname.encode())
        while True:
            data = f.read(BUFSIZE)
            if not data:
                break
            send(sock, data)

    sock.close()

fnames = [
    '1.jpg',
    '2.jpg',
    '3.jpg',
    '4.jpg',
]

def main():
    for fname in fnames:
        send_file(fname)

if __name__ == '__main__':
    main()

收件人：

from __future__ import print_function
import socket
from struct import unpack

HOST = '10.0.0.2'
PORT = 12345
BUFSIZE = 4096


class Receiver:
    ''' Buffer binary data from socket conn '''
    def __init__(self, conn):
        self.conn = conn
        self.buff = bytearray()

    def get(self, size):
        ''' Get size bytes from the buffer, reading
            from conn when necessary 
        '''
        while len(self.buff) < size:
            data = self.conn.recv(BUFSIZE)
            if not data:
                break
            self.buff.extend(data)
        # Extract the desired bytes
        result = self.buff[:size]
        # and remove them from the buffer
        del self.buff[:size]
        return bytes(result)

    def save(self, fname):
        ''' Save the remaining bytes to file fname '''
        with open(fname, 'wb') as f:
            if self.buff:
                f.write(bytes(self.buff))
            while True:
                data = self.conn.recv(BUFSIZE)
                if not data:
                    break
                f.write(data)


def main():
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    try:
        sock.bind((HOST, PORT))
    except socket.error as err:
        print('Bind failed', err)
        return

    sock.listen(1)
    print('Socket now listening at', HOST, PORT)
    try:
        while True:
            conn, addr = sock.accept()
            print('Connected with', *addr)
            # Create a buffer for this connection
            receiver = Receiver(conn)
            # Get the length of the file name
            name_size = unpack('B', receiver.get(1))[0] 
            # Get the file name itself
            name = receiver.get(name_size).decode()
            print('name', name)
            # Save the file
            receiver.save(name)
            conn.close()
            print('saved\n')

    # Hit Break / Ctrl-C to exit
    except KeyboardInterrupt:
        print('\nClosing')

    sock.close()

if __name__ == '__main__':
    main()

文件传输正常，并且没有问题。现在，我想在发送所有文件后发送一个简单的字符串，例如“ finish”，以便接收者理解传输已完成，并且它将基于此完成消息来执行其他一些任务（但是，它仍然可以同时接收消息）时间）。

我试图通过在发送方代码中添加另一个名为sendMessage()的函数以及在接收方中添加一个名为recvMessage()的函数来做到这一点。这是更改后的代码：

发件人：

from __future__ import print_function
import socket
from struct import pack

HOST = '10.0.0.2'
PORT = 12345
BUFSIZE = 4096
BUFFER_SIZE = 1024
MESSAGE = "Finish!"

def send(sock, data):
    while data:
        sent = sock.send(data)
        data = data[sent:]

#Updated part for sending message
def sendMessage(message):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((HOST, PORT))
    sock.send(message)
    data = sock.recv(BUFFER_SIZE)
    sock.close()
    print ("received data:", data)

def send_file(fname):
    with open(fname, 'rb') as f:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        try:
            sock.connect((HOST, PORT))
        except socket.error as err:
            print(err, HOST, PORT)
            sock.close()
            return

        # Send the file name length & the filename itself in one packet          
        send(sock, pack('B', len(fname)) + fname.encode())
        while True:
            data = f.read(BUFSIZE)
            if not data:
                break
            send(sock, data)

    sock.close()

fnames = [
    '1.jpg',
    '2.jpg',
    '3.jpg',
    '4.jpg',
]

def main():
    for fname in fnames:
        send_file(fname)
    sendMessage(MESSAGE)

if __name__ == '__main__':
    main()

接收方：

from __future__ import print_function
import socket
from struct import unpack

HOST = '10.0.0.2'
PORT = 12345
BUFSIZE = 4096
BUFFER_SIZE = 20

class Receiver:
    ''' Buffer binary data from socket conn '''
    def __init__(self, conn):
        self.conn = conn
        self.buff = bytearray()

    def get(self, size):
        ''' Get size bytes from the buffer, reading
            from conn when necessary 
        '''
        while len(self.buff) < size:
            data = self.conn.recv(BUFSIZE)
            if not data:
                break
            self.buff.extend(data)
        # Extract the desired bytes
        result = self.buff[:size]
        # and remove them from the buffer
        del self.buff[:size]
        return bytes(result)

    def save(self, fname):
        ''' Save the remaining bytes to file fname '''
        with open(fname, 'wb') as f:
            if self.buff:
                f.write(bytes(self.buff))
            while True:
                data = self.conn.recv(BUFSIZE)
                if not data:
                    break
                f.write(data)

#Updated part for receiving message
def recvMessage(conn):
    while 1:
        data = conn.recv(BUFFER_SIZE)
        if not data: break
        print("received data:", data)
        conn.send(data)  # echo


def main():
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    try:
        sock.bind((HOST, PORT))
    except socket.error as err:
        print('Bind failed', err)
        return

    sock.listen(1)
    print('Socket now listening at', HOST, PORT)
    try:
        while True:
            conn, addr = sock.accept()
            print('Connected with', *addr)
            # Create a buffer for this connection
            receiver = Receiver(conn)
            # Get the length of the file name
            name_size = unpack('B', receiver.get(1))[0] 
            # Get the file name itself
            name = receiver.get(name_size).decode()
            print('name', name)
            # Save the file
            receiver.save(name)
            conn.close()
            print('saved\n')

    recvMessage(conn)
    # Hit Break / Ctrl-C to exit
    except KeyboardInterrupt:
        print('\nClosing')

    sock.close()

if __name__ == '__main__':
    main()

但是运行完这些代码后，发送者和接收者在4个文件完全传输后都将冻结，并且什么也没有发生。怎么了，我该怎么办？

Answer 1

我怀疑您是在这里缓冲的牺牲品：

def sendMessage(message):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((HOST, PORT))
    sock.send(message)
    data = sock.recv(BUFFER_SIZE)
    sock.close()
    print ("received data:", data)

您执行send，然后立即尝试recv。除了流连接倾向于缓冲以避免避免过多的数据包开销外，很可能是，您实际上还没有发送任何东西，服务器看不到任何东西，因此它没有响应，并且双方都在等待数据。 >

这里最简单的解决方案是在发送消息后关闭发送侧端口以进行写入，这会强制输出最后的数据并使接收者知道您已完成操作：

def sendMessage(message):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((HOST, PORT))
    sock.sendall(message)          # sendall makes sure the *whole* message is sent
    sock.shutdown(socket.SHUT_WR)  # We're done writing
    data = sock.recv(BUFFER_SIZE)
    sock.close()
    print("received data:", data)

在接收方，您有一个更大的问题：在尝试接收之前先关闭连接：

    while True:
        conn, addr = sock.accept()
        print('Connected with', *addr)
        # Create a buffer for this connection
        receiver = Receiver(conn)
        # Get the length of the file name
        name_size = unpack('B', receiver.get(1))[0] 
        # Get the file name itself
        name = receiver.get(name_size).decode()
        print('name', name)
        # Save the file
        receiver.save(name)
        conn.close()       # Closed here!!!
        print('saved\n')

        recvMessage(conn)  # Used again here!!!

因此在close调用之后将recvMessage移到use setsockopt上将recvMessage更改为turn on TCP_NODELAY，这样就不会发生缓冲（否则回声back可能最终会无限期地缓冲，尽管关闭发送方以进行写入确实意味着您很可能检测到发送方已完成并退出循环然后关闭连接，因此只要没有TCP_NODELAY，它就可以正常工作，只要发件人不希望收到数据并进一步响应）：

def recvMessage(conn):
    # Disable Nagle algorithm so your echoes don't buffer
    conn.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
    while 1:
        data = conn.recv(BUFFER_SIZE)
        if not data: break
        print("received data:", data)
        conn.sendall(data)  # echo using sendall, again, to ensure it's all really sent