between two systems, with and without ssh tunneling
To check if a TCP connection exists, run
netcat -l -p 9999
on the receiver (to make sure the port is not in use yet) and
echo hallo | netcat $RECEIVER_IP 9999
on the sending system.
In case you have not opened port 9999, the firewall of the receiver will typically block this connection.
If you want to check the sending of TPC packets through an ssh tunnel (e.g., if the receiver is only visible behind a login node), you may establish the port connection by running
ssh -L 9999:$RECEIVER_IP:9999 $RECEIVER_LOGIN_NODE -nNT &
on the sender before starting netcat. The $RECEIVER_IP in the netcat call
then becomes localhost.
for the current setup (opened port 9999 on receiver for connections from sender), execute
python3 RTTTest.py -r -p 9999 -s 1000,10000
on the receiver and
python3 RTTTest.py -r $RECEIVER_IP -p 9999 -s 1000,10000
on the sender. The last numbers specify the data size to test (in bytes).