Socket Programming

Socket Programming

What’s a socket ?

An endpoint for communication or an Interprocess communication(IPC) method or where two parts can fit (2 way communication) (or in unix a file descripter indeed).

A file descripter ? Create a socket (with socket() system call) Get the PID (getpid() system call) Put some wait with any input Run the command -

Linux:

/proc/<PID>/fd 

Mac:

ls -p <PID>

Types of Socket

2 main sockets used in communication are “SOCK_STREAM” and “SOCK_DGRAM” or “Stream socket” and “Datagram Socket”.

1. Stream Sockets :- Reliable , Data reaches in sequence in which sent, error-free. Uses TCP. Ex.-
   • Browsers uses HTTP and HTTP uses Stream socket
   • telnet or ssh applications
2. Datagram Sockets :- Connectionsless ? Data Might reach , might not. When all data reaching is not necessary (like video calls, some live streams). Uses UDP.

Why Datagrams ? Speed, Faster than stream socket. fire-and-forget.

Ex.-

• Games , video conferencing etc.
• Some file transfer protocols like tftp
• dhcpcd (a DHCP client)

Wait ? but the last 2 require no data loss ?

Sends the package until it gets acknowledge of recieving in every 5 sec or some time interval.