Communicating On the Internet

Email Clients and Servers:
Anyone who has ever received an email in their lifetime has used an email client which can be either hardware or software based. The client is what lets you perform tasks like reading and sending email messages or downloading attachments. The email client also communicates with email servers which are responsible for getting the messages in emails to their destinations. Once the client has the information that it needs it can streamline processes.
How Email Is Delivered over the Internet
After hitting send the email client connects to a Simple Mail Transfer Protocol (SMTP) server for your email domain. Your email domain is the part of your email address that comes after the @ symbol. the SMTP is a set of rules for handling outgoing email. The email client tells the server who the email is from and who the email needs to go to.Then the SMTP server looks at the domain of the address that the email is being sent to and has the Domain Name System (DNS) ask for the IP address of the domain. Once that information has been maintained the SMTP connects with that domain and passes the message to its SMTP server. The SMTP server then passes the email to the incoming-mail server for delivery. The two types of incoming-mail servers are POP3 and IMAP. When you get an incoming email from a POP3 server, you download it from the server onto the computer you are using, but if you get email from an IMAP server, the email stays on the server utnil you delete it. Some POP3 clients offer a way to leave the mail on the server. If you use a web-based system for email then your email is handled by a web server, because it is online. All emails are sent as text only. The attachments of emails are only converted back from text once they arrive at their destination.
How Instant Messaging Works
Instant Messaging (IM) has been around since about 1990. It was an alternative to chat rooms for those who wanted to talk in real time over the Internet. Today IM software can allow much more than chatting with other Internet users. You can send and receive files, create chat rooms, and send some messages to and from a cell phone. Before using IM a client software for whatever service you want to use must be downloaded. Once it is installed in your computer, you can run the client so it will connect to the server. After connecting to the server you may either log in or create a new account. Once logged in, the client sends the server your IP address, and the server checks your list against the list of users who are online. Then it sends your client the IP address and port information for any contacts of yours who are online. It also sends your information to any users that have you as a contact. The server then stays out of the IM process. The client has all of the information necessary. The next thing the server will do is end your session when you log off, and let others know that you have gone offline. Many types of IM software are free, and many websites have built-in IM applications.