tools/hexnet: Move the TCP reading portion to a thread

This was too straight-forward to not just do it when I previously worked
on hexnet. Why didn't I just do it? Idk.

src/tools/hexnet.cpp

@@ -160,7 +160,8 @@ int main(int argc, char* argv[]){
             return EXIT_RUNTIME;
         }
 
-        readFromTCPSocket(tcpSocket, mtu);
+        std::thread threadReadTCP = std::thread(readFromTCPSocket, tcpSocket, mtu);
+        threadReadTCP.join();
 
         delete tcpSocket;
         return EXIT_SUCCESS;