If the server is located on a LAN with an address range which is published on the Internet it would suffice to setup a fully qualified host name (FQHN) and ensure that it is added to DNS. People would then be able to reach the machine through the URI http://<FQHN>:7778/forms/frmservlet?form=menu_tree.fmx
In real life, the server is probably located in a LAN with [url http://en.wikipedia.org/wiki/Private_network]private address ranges and made accessible through a firewall. In those cases, you need want to direct the traffic to a reverse proxy which hides the forms server from the real world.
Read through the [url http://docs.oracle.com/cd/B14099_19/core.1012/b13998/toc.htm]Enterprise Deployment guide for recommendations on network topology setup. Take this subject seriously and involve staff with the required expertise as you don't want to open up your server for the outside world without the necessary security in place. That said, from a security point of view, I would not go live with Application Server 10g anymore as Oracle does not provide security patches anymore for this obsolete version.