buffer.c

 /*
             * Due to a bug in Windows Sockets (observed on NT and Windows
             * 2000) it may be necessary to retry the send. The issue is that
             * on blocking sockets send/WSASend is supposed to block if there
             * is insufficient buffer space available. If there are a large
             * number of threads blocked on write due to congestion then it's
             * possile to hit the NT/2000 bug whereby send returns WSAENOBUFS.
             * The workaround we use is to retry the send. If we have a
             * large buffer to send (>2k) then we retry with a maximum of
             * 2k buffer. If we hit the issue with <=2k buffer then we backoff
             * for 1 second and retry again. We repeat this up to a reasonable
             * limit before bailing out and throwing an exception. In load
             * conditions we've observed that the send will succeed after 2-3
             * attempts but this depends on network buffers associated with
             * other sockets draining.
             */
            if (WSAGetLastError() == WSAENOBUFS) {
                if (llen > MAX_BUFFER_LEN) {
                    buflen = MAX_BUFFER_LEN;
                    chunkLen = MAX_BUFFER_LEN;
                    llen = MAX_BUFFER_LEN;
                    continue;
                }
                if (retry >= 30) {
                    JNU_ThrowByName(env, JNU_JAVANETPKG "SocketException",
                        "No buffer space available - exhausted attempts to queue buffer");
                    if (bufP != BUF) {
                        free(bufP);
                    }
                    return;
                }
                Sleep(1000);
                retry++;
                continue;
            }