文件传输完成后发送消息

Question

我不熟悉套接字编程。我正试图从一台主机向另一台主机发送4个文件。代码如下：

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()

接收器：

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()

文件传输工作正常，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，如“finish”，以便接收方理解传输已完成，并根据此finish消息执行一些其他任务（但是，它仍然可以同时接收消息）

我试图通过向发送方代码添加另一个名为sendMessage()的函数和向接收方添加一个名为recvMessage()的函数来实现这一点。以下是更改后的代码：

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()

接收器：

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()

但是在运行这些代码之后，发送方和接收方在4个文件的完整传输之后都冻结了，什么也没有发生。出了什么问题，我该怎么做

Answer 1

我怀疑你是这里缓冲的牺牲品：

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)

执行send，然后立即尝试recv。除了流连接倾向于缓冲以避免过多的数据包开销，所以很有可能，您实际上还没有发送任何内容，服务器没有看到任何内容，因此它没有响应，并且双方都被阻止等待数据

这里最简单的解决方案是在发送消息后关闭发送端端口进行写入，这会强制输出最后的数据，并让接收方知道您已经完成了：

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)

在接收器端，您有一个更大的问题：在尝试接收之前关闭连接：

    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recvMessage调用之后移动close，并将recvMessage更改为use ^{}更改为turn on ^{}，这样就不会发生缓冲（否则回显可能会无限期地进行缓冲，尽管关闭发送方进行写入意味着您可能会检测到发送方已完成并退出循环，然后关闭连接，因此，只要发送方不希望接收数据并进一步响应，它在没有TCP_NODELAY的情况下也可以正常工作）：

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