As a system administrator, it is often necessary to do a "sanity check" from time to time. Most problems become simple when you can break them down into their various parts. Often, though, we take the services we use for granted. We know that the web server is running, email "just works"...right??? Using some of the tricks below, you can verify that these services, in fact work, as you assumed and save yourself a lot of time and trouble.
telnet server 80 GET / HTTP/1.1
telnet server 25 Trying X.X.X.X... Connected to localhost. Escape character is '^]'. 220 sever ESMTP Exim 4.69 Wed, 07 Jan 2009 21:53:57 -0600 HELO foobar.com 250 server Hello localhost [127.0.0.1] mail from: <a href="mailto:firstname.lastname@example.org">email@example.com</a> 250 OK rcpt to: <a href="mailto:firstname.lastname@example.org">email@example.com</a> 250 Accepted data 354 Enter message, ending with "." on a line by itself payload . 250 OK id=1LKlz9-0000cW-Tz quit 221 server closing connection Connection closed by foreign host.
telnet mail.foobar.com 110 Trying X.X.X.X... Connected to mail.foobar.com. Escape character is '^]'. +OK The Microsoft Exchange POP3 service is ready. USER username +OK PASS password +OK User successfully logged on. STAT +OK 6 48274 LIST +OK 6 48274 1 11274 2 11269 3 4929 4 4461 5 13350 6 2991 . QUIT +OK Microsoft Exchange Server 2007 POP3 server signing off. Connection closed by foreign host.
I am sure most of these are old-hat to many of you, what other "stupid telnet tricks" do you have?