RSEG1242 “Daemon failed to launch server on <host> using port <port>”

Problem

In Developer for z/OS®, the message

RSEG1242 Daemon failed to launch server on <host> using port <port>

can have the following details:

When you see CONNECTION REFUSED, then RSE (Remote System Explorer) daemon is not active.

When you see SERVER FAILURE, with a message, then your client has contacted the host but became disconnected.

For CONNECTION REFUSED you should do the following things:

Check the RSED job output in SDSF (Spool Display and Search Facility). The RSE daemon is not using the port specified by the client, or RSE daemon is not running.
Check console message FEK002I (system log or RSE daemon job output). A firewall or other network issue is blocking the client from accessing the RSE daemon port. (Port 0 in the RSEG1242 message normally indicates the RSE daemon.)
Try telnet from the client machine to the RSE daemon port (the connection will hang for 30 seconds if successful, but a firewall should display a message).
```
telnet <host> <port>
```
The client can access RSE daemon, but not the RSE server due to firewall issues. (This is typically indicated by a non-zero port number in the RSEG1242 message.)
Alter the _RSE_PORTRANGE in /etc/rdz/rsed.envvars.

For SERVER FAILURE: <message>: The details show the error message shown in rseserver.log, but only if the RSE daemon or server was reached:

ERROR RseDaemon: server failure: password revoked

In this case, view detailed host logs to see which part of the code failed.
Set debug_level=2 in /etc/rdz/rsecomm.properties and restart the RSE daemon, or use the operator commands to dynamically activate tracing:
```
F RSED,APPL=RSL ON
```
and
```
 F RSED,APPL=RCL ON
```
After recreating the problem, customize and run FEK.SFEKSAMP(FEKLOGS). Create a service request PMR and send the output to IBM®.

None.