Listen.exe. A small utility to listen and reply on multiple TCP ports

Listen.exe is great for testing whether a system is accessible from another system.  It creates TCP listeners on whatever ports you specify (they run concurrently), and responds with small simple messages you write when a connection is made.  Great troubleshooting tool.  Single executable with no DLLs or installer.
https://www.allscoop.com/downloads/listen.zip