python：调用socket.recvfrom()两次
我正在编写两个 python 脚本，使用 python sockets 通过 UDP 进行通信。这是代码的相关部分，
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind((HOST, PORT))
s.setblocking(True) #I want it to be blocking
#(...)
(msg, addr) = sock.recvfrom(4)
#(...)
(msg2, addr2) = sock.recvfrom(2)
我希望接收被阻塞，并且在读取第一个 4 字节部分之前我不知道整个消息的大小。上面的代码在 sock.recvrfom(2) 部分被阻止，而修改后，用一个 sock.recvfrom 而不是两个工作正常：
(msg, addr) = sock.recvfrom(6) #works ok, but isn't enough for my needs
知道如何方便地阅读传入的数据分为两部分，或者为什么代码不能按预期工作？
I am writing two python scripts to communicate over UDP using python sockets. Here's the related part of code
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind((HOST, PORT))
s.setblocking(True) #I want it to be blocking
#(...)
(msg, addr) = sock.recvfrom(4)
#(...)
(msg2, addr2) = sock.recvfrom(2)
I want the receiving to be blocking and I don't know the size of the whole message before I read the first 4-byte part. The above code becomes blocked on the sock.recvrfom(2) part, whereas modified, with one sock.recvfrom instead of two works alright:
(msg, addr) = sock.recvfrom(6) #works ok, but isn't enough for my needs
Any idea how I can conveniently read the incoming data in two parts or why the code doesn't work as expected?
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socket.recvfrom(size)将（对于 UDP 套接字）读取一个数据包，最多size字节。多余的数据将被丢弃。如果你想接收整个数据包，你必须传递一个更大的 bufsize，然后以位为单位处理数据包（而不是尝试以位为单位接收它）。如果你想要一个更方便、更稳定的网络 I/O 接口，考虑一下Twisted。
socket.recvfrom(size)will (for UDP sockets) read one packet, up tosizebytes. The excess data is discarded. If you want to receive the whole packet, you have to pass a larger bufsize, then process the packet in bits (instead of trying to receive it in bits.)If you want a more convenient, less fickle interface to network I/O, consider Twisted.
从 UDP 套接字读取整个数据报出队。
Read from UDP socket dequeues the whole datagram.
UDP 是一种基于消息的协议。
recvfrom将读取最初发送的整个消息，但如果缓冲区不够大，则会抛出异常：所以我不确定为什么你如果最初发送的是 6 字节消息，则会挂在第二个
recvfrom上。您应该在第一个recvfrom上抛出异常。也许发布一个实际工作的客户端和服务器程序的最小示例。UDP is a message-based protocol.
recvfromwill read the entire message that was originally sent, but if the buffer isn't big enough, it will throw an exception:So I am not sure why you would hang on the 2nd
recvfromif a 6-byte message was originally sent. You should throw an exception on the firstrecvfrom. Perhaps post an actual working, minimal example of the client and the server program.