Python socket recv 正在拆分收到的消息

Question

我正在 Python 和 Java 进程之间进行套接字通信。我正在尝试使用 java 发送一个 int 并在 Python.

中接收它

Java 方（发件人）：

        ServerSocket ss = new ServerSocket(6666);
        Socket s = ss.accept();

        DataOutputStream dos = new DataOutputStream(s.getOutputStream());
        
        final int numberToSend = 512;

        dos.writeInt(numberToSend);  //In big endian        
        dos.flush();

Python 方（接收方）：

        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.connect(('127.0.0.1', 6666))

        while True:
            data_received = s.recv(4)
            int_received = int.from_bytes(data_received, byteorder='big')
            print("Received:", data_received, "Number:", int_received)
            
            do_other_stuff(int_received)

我很确定 Java 端工作正常。 dos.size() 给出 4 个字节。

但是，从 Python 的角度来看，data_received 似乎被分成两部分。对于每个周期，打印给出：

Received: b'\x00' Number 0
Received: b'\x00\x02\x00' Number 512

预期为 Received: b'\x00\x00\x02\x00' Number 512。随着消息拆分，它会干扰 do_other_stuff。 sys.getsizeof(data_received) 分别为第一部分和第二部分给出 18 和 20。

我也试过 int_received = struct.unpack("!i", data_received)[0] 但它给出了 struct.error: unpack requires a buffer of 4 bytes，因为消息有 1 个和 3 个字节。

我做错了什么？

Answer 1

我猜你没有做任何逻辑上的错误，但这似乎是 TCP 的工作方式。在documentation about using sockets中，虽然需要一定数量，但接收处于循环等待获取预期数据量的状态。

尝试做同样的事情。 IE。在伪代码中：

    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect(('127.0.0.1', 6666))

    data_received = b""
    long_received = 0
    while True:
        while long_received < 4:
            data_received += s.recv(4-long_received)
            long_received = len(data_received)
        int_received = int.from_bytes(data_received, byteorder='big') 
        print("Received:", data_received, "Number:", int_received)
        do_other_stuff(int_received)
        data_received = b""
        long_received = 0

编辑：添加了 Remy Lebeau 的注释。谢谢。

编辑 2：正如用户 user207421 所说，这是 TCP 的行为，而不是 Python。谢谢，对我来说绝对是新的。 :D

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