True Telnet?

[Chris Morrow]

Hello;

I am trying to emulate a true telnet hyper terminal within a flow. The connection is made on port 23 but there is no response from the server. Communication between the telnet server works properly in Teraterm or a hyper terminal, but within my flow I get no response from the server. In Wireshark I can see the server protocol listed as TENET, whereas node-red is listed as TCP. I have added a <CR> as suggested with this forum with no luck.

When the connection is first made with the server, it returns unprompted text strings indicating the server system health.  I do not see these appear or any response in the node-red debug. I am overlooking some glaring error. Any suggestions?

BTW I am microwave communications engineer not a programmer, so just trying to learn some new tools.

I have attached the flow.

Chris

[Mark Setrem]

If you look at the wikipedia page for telnet it has a section on telnet data format and the differences between it and raw TCP https://en.wikipedia.org/wiki/Telnet.

Have you tried the alternate options in the TCP-In node setup?   I can connect to a "telnet" session on my router by using the option "Output"  "stream of" "Buffer" payload(s)

[Chris Morrow]

So are you inferring to set up a raw tcp connection with the correct message terminations?

Does anyone have an example they could post?

C

[Walter Kraembring]

Dave C helped me with this one some time ago,,,it is working fine, maybe could help. It is a bit tailored to a specific host but I think you get the ideas.

Kind regards, Walter

[{"id":"6f7de61.346b118","type":"debug","z":"6b5ceb9e.2f8654","name":"","active":true,"console":false,"complete":false,"x":690,"y":520,"wires":[]},{"id":"f98c45f7.6bd728","type":"tcp request","z":"6b5ceb9e.2f8654","server":"192.168.10.253","port":"8005","out":"sit","splitc":"0","name":"","x":730,"y":360,"wires":[["d214d069.7875a"]]},{"id":"6186a1c.e35ed6","type":"inject","z":"6b5ceb9e.2f8654","name":"connect & subscribe","topic":"","payload":"","payloadType":"str","repeat":"","crontab":"","once":false,"x":250,"y":80,"wires":[["2c21e3bd.be55ec"]]},{"id":"d214d069.7875a","type":"function","z":"6b5ceb9e.2f8654","name":"msg.payload = msg.payload.toString(); return msg;","func":"msg.payload = msg.payload.toString();\nreturn msg;","outputs":1,"noerr":0,"x":810,"y":440,"wires":[["6f7de61.346b118"]]},{"id":"2c21e3bd.be55ec","type":"function","z":"6b5ceb9e.2f8654","name":"msg.payload = '\\n'; node.send(msg); msg.payload = 'subscribe\\n'; node.send(msg);","func":"msg.payload = '\\n';\nnode.send(msg);\nmsg.payload = 'subscribe\\n';\nnode.send(msg);","outputs":1,"noerr":0,"x":460,"y":160,"wires":[["f98c45f7.6bd728"]]},{"id":"c55f7af2.169fc8","type":"inject","z":"6b5ceb9e.2f8654","name":"quit & disconnect","topic":"","payload":"","payloadType":"str","repeat":"","crontab":"","once":false,"x":240,"y":220,"wires":[["4111f34e.a8534c"]]},{"id":"4111f34e.a8534c","type":"function","z":"6b5ceb9e.2f8654","name":"msg.payload = 'quit\\n'; node.send(msg);","func":"msg.payload = 'quit\\n';\nnode.send(msg);\n","outputs":1,"noerr":0,"x":320,"y":300,"wires":[["f98c45f7.6bd728"]]}]

 

[Chris Morrow]

Walter;

I tried you suggestion with not much luck. I seem to be getting some type of header query, which node-red needs to provide a response, but does not.

 

I am expecting this response:

(/dev/ttypf)

Enhanced, Release 3.0.2 (3189)

Copyright 2002-2015 

All rights reserved.

Username :

Password :

Instead I get this:

see attached

[Walter Kraembring]

Yes, but my example was for a specific server expecting a certain init. You have to modify the content in the first function node so it fits the requirements of the host you are connecting to

[Chris Morrow]

Yes, I saw that and made those modifications. After some research I see the telnet session begins by negotiating transmission parameters at which node-red did not respond. I believe this is my error.