UDP (User Datagram Protocol)

• No connection setup between client and server
  • No hand shaking
  • The sender explicitly attaches their sending port from the packet
  • The receiver reads this value in the packet to determine who ‘sent’ it
• Fire and forget - no certainty that the data is received correctly, in correct order, or if received at all.
• The server might not even be on at all!

Pseudo Code

• Create socket
  • Bind port (Server)
• Loop
  • Send UDP datagram to known port
  • Read UDP datagram
• Close socket

TCP (Transmission Control Protocol)

• Client contacts the server to establish a connection.
• Server then creates a new socket to communicate with the client - Different socket for welcoming than for connection
• Reliable - Packets will arrive in order, and if packets are lost, they will be retransmitted

Pseudo Code

• Create socket
• Connect to server (Client only)
• Bind port (Server only)
• Listen for requests (Server only)
  • Accept request
• Communicate
• Close

Concurrent TCP Servers

Connection requested are performed in a fork, rather than the main process, so the main process can continue to wait for new connections.