Step 1: Portforwarding Learn how to RSPS - YouTube
Step 2: Make a no ip , add a host and in duc 3.0 or whatever make sure ur host is checked and click the refresh
Step 3: put ur no ip in client.java (client sided) SAVE AND COMPILE
Step 4: right click ur entire client folder and click "add to (your client folder name)"
Upload that winrar file to ********** or something
Step 5: make sure ur source is running
step 6: make sure ur no ip host isn't expired bc u have to renew it every month , and u may need to go back and portforward again ( just change the ip to whatever it is in ur cmd ipconfig ) because it could change if ur router reset
If its still not working then u obviously portforwarded wrong
Hope my spoonfeeding helped