TCP between two computer in a diffrent network using Java -

i wrote server-client chatprogram lets send messages between 2 computer in same network. im trying work if computer in diffrent networks. cofigured router forward request cetain port pc. guessing client pc needs this? connect client use code:

static socket smtpsocket = null; smtpsocket = new socket(); smtpsocket.connect(new inetsocketaddress("-server ip-", port)); 

server:

echoserver = new serversocket(); echoserver.bind(new inetsocketaddress("-server ip", port)); 

to send/receive data use printstream/datainput stream on both side:

is = new datainputstream(clientsocket.getinputstream()); os = new printstream(clientsocket.getoutputstream()); 

but nothing happens. have configure printstreams send data specic computer?