libnodave times out whenever I try to `writeBytes`

Question

I am using the libnodave library to communicate with a Siemens S7 PLC. It works fine, until I try to write bytes. I almost always times out.

The code I have to connect:

fds.rfd = libnodave.openSocket(port, address.ToString());
fds.wfd = fds.rfd;

if (fds.rfd > 0) {
    di = new libnodave.daveInterface(fds, "IF1", 0, libnodave.daveProtoISOTCP, libnodave.daveSpeed187k);
    di.setTimeout(10000000);

    dc = new libnodave.daveConnection(di, 0, 0, 2);

    if (0 == dc.connectPLC()) {
        _status.connected = true;
    }
}

and to write the bytes (in another method, called in a later stage):

dc.writeBytes(libnodave.daveDB, datablock, address, bytestowrite, buftosend);

which almost always returns -1025 (timeout).

Changing the timeout, or moving the connect routine directly before the writing has no effect.

Answer 1

As always as things get weird, and there is multithreading going on, there is the problem.

I was calling writeBytes while there was a call of readBytes still going on, messing up the results.

Adding a mutex and better timing fixed it.