c++ - Proper way to close a blocking UDP socket

Question

I have a C++ object that creates a thread to read from a blocking UDP socket:

mRunning.store(true);
while (mRunning.load(boost::memory_order_consume)) {
    ...
    int size = recvfrom(mSocket, buf, kTextBufSize , 0,
                        (struct sockaddr *) &packet->mReplyAddr.mSockAddr, (socklen_t*)&packet->mReplyAddr.mSockAddrLen);

    if (size > 0) {
        //do stuff
    }
}
return 0;

(mRunning is a boost::atomic) The object's destructor is called from another thread and does this:

mRunning.store(false);  
#ifdef WIN32
    if (mSocket != -1) closesocket(mSocket);
#else
    if (mSocket != -1) close(mSocket);
#endif
pthread_join(mThread, NULL);

This seems to work, but one of my colleagues suggested that there might be a problem if recv is interrupted in the middle of reading something. Is this thread safe? What's the correct way of closing a blocking UDP socket? (Needs to be cross-platform OSX/Linux/Windows)

Answer 1

There could be a lot of different problems. Moving my application from one FreeBSD version to another I found that such close() worked normally on older kernel and just hung close() until something returned from recv() on newer. And OSX is FreeBSD based :)

Portable way of closing sockets from different thread is to create pipe and block not in recv(), but in select(). When you need to close socket, write something to pipe, select() will unblock and you can safely do close().