What is the difference between TCP and UDP? Where is each used?

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are two main transport layer protocols in a network.

Main differences:

• TCP is connection-oriented, provides reliable data delivery, error checking, packet order, and flow control.
• UDP is connectionless, does not guarantee delivery, order, or integrity, but operates faster and with less overhead.

Where TCP is used:

• Web servers (HTTP/HTTPS)
• Email (SMTP, IMAP)
• FTP
• Any applications where reliable data transfer is important

Where UDP is used:

• Video conferencing and VoIP, where speed and minimal latency are crucial, and packet loss is acceptable
• Online gaming for transmitting game states
• DNS queries
• Multimedia streaming

Example: if you are developing a chat application where message reliability is important, it is better to use TCP. If you need to stream video with minimal delay, UDP is preferable.