I've been in the same situation as you in the past and have done this by binding the to port that I want to remote hardware to respond to, without ofxPoco.
Here I send to port 5555 of the device, the device will reply to my IP address on port 5556.
std::string ip = "192.168.130.255";
buf = 'P';
buf = 'B';
if (m_udpSend.Send(buf, 2))
printf("Sent %s to IP: %s\n", buf, ip.c_str());