I am having issue making remote telnet connection to JLink GDBServer in order to receive RTT data. Specifics:

Raspberry Pi/Ubuntu Server 20.04

• Development station running gdb-multiarch V12.0.90
  

PC/Windows 10

• Running JLink GDBServer V7.70
  
• USB Connection to a Nordic nRF52840 development board
  

Problem Description

• I am able to debug programs across the remote connection, as I have unchecked the JLink GDBServer Localhost only checkbox.
  
• I can connect to the JLink GDBServer telnet port on the Windows side using RTT Viewer, PuTTY and the Windows telnet utility.
  
• I cannot connect to the JLink GDBServer telnet port from the Raspberry Pi using the Linux telnet utility. I get a connection refused error.
  
• I have worked with the Windows firewall to allow all incoming connections during these tests. This was not necessary to do debugging though.
  

I'm at a bit of a loss as to what might be going on. Is the JLink GDBServer program prepared to accept remote connections to the telnet output port?

I was able to work around the issue by creating a port forwarding rule on the Windows PC:

netsh interface portproxy add v4tov4 listenport=19020 connectaddress=127.0.0.1 connectport=19021

My remote connection connects to port 19020 on the PC where GDB Server is running and is forwarded to 19021. Telnet data now flows freely from GDB Server to my Linux telnet client.

My conclusion at this point is that GDB Server is not accepting remote connections on the telnet port for some reason. GDB Server won't accept remote connections for debugging unless specifically enabled.

SEGGER Team,
Is the behavior described accurate and intentional?