Hyper Text Transfer Protocol (HTTP)
The Hyper Text Transfer Protocol provides a standard for communication between web browsers and the server. It is one of the most widely used protocol on the Internet for requesting documents such as web pages and images.
Example : www.example.com
File Transfer Protocol (FTP)
The File Transfer Protocol provides a standard for transferring files between two computers on the network. FTP is most widely used in carrying out upload/download operations between a server and a workstation.
Simple Mail Transfer Protocol (SMTP)
The Simple Mail Transfer Protocol provides a standard for sending e-mails from one server to another. Most e-mail systems that send mail over the Internet use SMTP to exchange messages between the server.
Post Office Protocol 3 (POP3)
Post Office Protocol (POP) offers a way of interacting with mail servers that date back to a very different Internet than we use today. Computers tended to not have permanent Internet access. Instead, you connected to the Internet, did what you needed to do, and then disconnected. Those connections were also pretty low bandwidth compared to what we have access to today.
Internet Messaging Access Protocol (IMAP)
IMAP stores all messages on the server. When you connect to an IMAP server, the client app lets you read those emails (and even downloads copies for reading offline), but all the real business happens on the server. When you delete a message in a client, that message is deleted on the server, so you don’t see it if you connect to the server from other devices. Send messages are also stored on the server, as is information about which messages have been read.
Telnet is a network protocol that allows you to connect to remote hosts on the Internet or on a local network. It requires a telnet client software to implement the protocol using which the connection is established with the remote computer.
In most cases telnet requires you to have a username and a Password to establish connection with the remote host. Occasionally, some hosts also allow users to make connection as a guest or public.
After the connection is made, one can use text based commands to communicate with the remote host. The syntax for using the telnet command is as follows:
telnet hostname or IP> port
Example:telnet 127.0.0.1 25
SSH (Secure Shell)
SSH is a protocol similar to telnet which also facilitates connection to remote hosts for communication. However, SSH has an upper hand over telnet in terms of security. Telnet was primarily designed to operate within the local network and hence does not take care of security. On the other hand SSH manages to offer total security while connecting to remote hosts on a remote network or Internet.
Akin to telnet SSH also uses a client software and requires a username and Password to establish the connection with the remote host.