Communication requires protocols (rules) so that those involved in the communication understand how to interact. In the world of technology this could be communication between two or more computers which means for example they may need to understand:
- Transmission speed
- Type of data to be shared
- How to share the data
Protocols for use over the Internet are generally published as RFCs (Request for Comments) by standards setting bodies such as the Internet Engineering Task Force (IETF).
TCP and UDP
Transmission Control Protocol (TCP) and User Datagram Protocol are communication protocols used to share data across a network such as the Internet.
TCP is connection oriented, it involves sender and receiver going through a handshake process and has error checking/error correction.
UDP is connectionless, it does not involve a handshake and does not have error correction (i.e. no guarantee of delivery. However, it is faster than TCP.
Example Protocols
There are many different types of protocols used over TCP and UDP. These include, but are not limited to:
| Protocol | Description | Port |
| HTTP | Hyper Text Transfer Protocol
Used for communication between web servers and clients |
80 |
| HTTPS | Hyper Text Transfer Protocol Secure
Same as above but uses secure encryption |
443 |
| FTP | File Transfer Protocol
Used to transfer files |
21 |
| SFTP | Secure File Transfer Protocol or SSH File Transfer Protocol
Same as above but uses secure encryption |
22 |
| SSH | Secure Shell
Allows for remote connection / remote command execution |
22 |
| NTP | Network Time Protocol
An NTP server provides time services to a client. |
123 |
| SMTP | Simple Mail Transfer Protocol
Used to send and receive emails |
25 |
| POP3 | Post Office Protocol version 3
Used by a client to download emails from a server |
110 |
| IMAP | Internet Message Access Protocol
Unlike POP3 it can be used by multiple clients and generally leaves the emails on the server |
143 |