How to set ros_master_uri to a port of a router ?

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Hi everyone, So I have a wam arm, whose ip is 192.168.1.31, which is connected to port 31 of a router with static ip address 164.67.192.135, and the wam arm is set as the ros master. So now I want to remote control this wam from another PC which is connected with another Ethernet cable (different with the router). But since the router provide a firewall for the wam behind it, I can't directly access the wam by setting the ros_master_uri as http://192.168.1.31:11311/ . however, I can still ssh into wam from the remote pc using port forwarding, I guess I have to do a similar thing when setting the ros_master_uri, but I don't know what the exact steps, any suggestions ?