A socket is one end-point of a communication link between systems. It's an abstraction in which your application can send and receive data over the network, in much the same way that your application can read and write to a file using a file handle.
An open socket is uniquely defined by a 5-tuple consisting of the following:
- Local IP address
- Local port
- Remote IP address
- Remote port
- Protocol (UDP or TCP)
This 5-tuple is important, as it is how your operating system knows which application is responsible for any packets received. For example, if you use two web browsers to establish two simultaneous connections to example.com on port 80, then your operating system keeps the connections separate by looking at the local IP address, local port, remote IP address, remote port, and protocol. In this case, the local IP addresses, remote IP addresses, remote...
