Telnet Servers and Clients
The oldest Telnet server, found on UNIX and Linux systems, is the venerable telnetd. Like most UNIX/Linux servers, telnetd isn't much to look at, so let's move over to the Windows world. Since Windows itself doesn't have a built-in Telnet server, we lean toward third-party server programs like freeSSHd. Note the name?freeSSHd, not "freeTelnet." As Telnet fades away and SSH becomes more dominant, it's hard to find a Telnet-only server these days. All of the popular Telnet servers are also SSH servers.
NOTE Some versions of Windows Server came with a rather poor Telnet server that only allowed a maximum of two client connections.
A Telnet client is the computer from which you log onto the remote server. Most operating systems have a built-in Telnet client that you run from a command prompt. The Telnet client built into Ubuntu Linux. Just open a terminal window and type telnet and the IP address of the Telnet server.
Command-prompt Telnet clients lack a number of handy features. They can't, for example, remember the IP addresses, user names, or passwords for Telnet servers, so every time you use Telnet, you have to enter all that information again. Third-party Telnet clients, such as the very popular PuTTY, store all this information and much more.
In this tutorial:
- TCP/IP Applications
- Transport Layer Protocols
- TCP
- UDP
- ICMP
- IGMP
- The Power of Port Numbers
- Registered Ports
- Connection Status
- Rules for Determining Good vs. Bad Communications
- Common TCP/IP Applications
- HTTP
- Publishing Web Pages
- Web Servers and Web Clients
- Secure Sockets Layer and HTTPS
- Telnet
- Telnet Servers and Clients
- Configuring a Telnet Client
- Rlogin, RSH, and RCP
- SSH and the Death of Telnet
- SMTP, POP3, and IMAP4
- Alternatives to SMTP, POP3, and IMAP4
- E-mail Servers
- FTP
- Passive vs. Active FTP