If the timeout means the runtime i.e. rmdstestclient exits after running for the specified amount of time. You can use -et <time>. For example:
./rmdstestclient -S ELEKTRON -f rics.txt -ct rssl -h 192.168.27.15 -p 14002 -u pimchaya -et 60 -v -X -d 2 -l stdout
According to my test with the command above, rmdstestclient will run 60 seconds before it exits.
Please note that you can find the rmdstestclient and other TREP tools information such as parameter, basic command etc in Demo_Tools_<ADS version>.pdf document. The file is available at <ADS package>/doc folder.