Overview: Sockets vs Streams

Socket represents a unique communication endpoint on the network. When your app needs to exchange data with another app, it creates a socket and uses it to connect to the other app’s socket. You can both send and receive data through the same socket. Each socket has an IP address and a port number (between 1 and 65535) associated with it. IP address uniquely identifies each computer on a given network and port number uniquely identifies a network socket on that computer.

Stream is a one-way channel through which data is transmitted serially. There are 2 types of streams: the ones into which you can write data, and the ones from which you can read. By itself, stream is just a buffer that temporarily holds data before or after its transmission. In order to actually deliver data somewhere meaningful, streams need to be tied to something (like a file, a memory location etc). In this tutorial, we’ll use streams that are paired up with sockets to allow our app to send data over network.

Overview: Bonjour

Bonjour is a protocol that allows devices or applications to find each other on the network. More precisely, it provides a way for an application to tell others what IP address and port they can connect to in order to communicate with it. In Bonjour terminology, such announcement is called publishing a service. Other apps can then look for services by browsing. Once an app finds a service that it would like to talk to, it resolves the service to find out what IP address and port number it needs to establish a socket connection to.

In the SDK, Bonjour can be used via NSNetServices and CFNetServices APIs.