I do not have wireshark and I do not control the client, however, the client is a Mirth interface engine. It is able to connect to my server and appears on their side to successfully transmit the messages. If they host their Mirth instance on Linux, however, I do receive their messages. Is there some setting for QTcpServer that needs to be set to accommodate a connection from a Windows box? The client side developer seems to think is has something to do with the way Windows does carriage return line feeds but I think it is lower level than that because I do not even get to the point where I read the message because the newConnection signal is never fired.