From Xojo Documentation
Any kind of communication requires that all parties involved agree on a method of communication and a language. For example, if you want to communicate with a friend, you might talk to them face to face, call them on the phone, or send them email. Both of you must be able to communicate using the same language or you won’t be able to communicate at all. Communications via the Internet works the same way. The language used is called a protocol. A protocol is simply an organized way of sending and/or receiving information.
If you are writing an app that will communicate with another application via TCP/IP (Transfer Control Protocol/Internet Protocol) for example, you will need to understand the protocol the other app will be expecting in order to communicate with it. For example, on the Internet, the protocol for the world wide web is called HTTP (HyperText Transfer Protocol), the protocol for sending email is called SMTP (Simple Mail Transfer Protocol), and a protocol for receiving email mail is called POP3 (Post Office Protocol 3). Complete descriptions of these Internet protocols and others are available on the Internet. The descriptions of these protocols are called RFCs (Request For Comments). The easiest way to find information on RFCs is to go search for “RFC”. This will give you a list of links to various web sites that explain all of the various Internet protocols.
If you are writing an app that communicates with other apps you have written, then you can define your own protocol. Your protocol will simply be a set of commands you define that allow the apps to understand what the other wants.
Limitations on Sockets in Web Applications
You cannot use a networking socket of any kind on a web page because the socket is really running on the server and would have no way to push its data back to the client browser to update the user interface. However, sockets that are a property of your App class will work.