cannot connect to a port

My droplet has debian os. I have a java application running which tries to exchange data with remote similar applications. This data exchange has previously worked across remote environments where each node has been a hardware node. It uses apache tribes package to exchange peer to peer messages over TCP.

I have set TCP port 4000 as a rule in my firewall and I have been expecting to be able to communicate with my application listening on that port. Netstat reports 4000 to be a listening port.

In the past with my application running on a dedicated remote server, I have been able to connect using telnet from a remote system (in which case my log files respond reporting junk data). Currently, telnet reports “?need to be connected first”

Also, from the droplet command line I issue: echo “some text” > /dev/tcp/127.0.0.1/4000 which invokes “connection refused”

If I use udp instead, there is no error, but still no indication that the data reached my application.

many thanks,