Bash/nc: netcat as a simple http/smtp client

gistfile1.txt

TALKING TO SERVERS
     It is sometimes useful to talk to servers “by hand” rather than through a user interface.  It can aid in troubleshooting, when it might be necessary to verify what data a server is sending in response to commands issued by the client.  For example, to
     retrieve the home page of a web site:

           $ printf "GET / HTTP/1.0\r\n\r\n" | nc host.example.com 80

     Note that this also displays the headers sent by the web server.  They can be filtered, using a tool such as sed(1), if necessary.

     More complicated examples can be built up when the user knows the format of requests required by the server.  As another example, an email may be submitted to an SMTP server using:

           $ nc [-C] localhost 25 << EOF
           HELO host.example.com
           MAIL FROM:<[email protected]>
           RCPT TO:<[email protected]>
           DATA
           Body of email.
           .
           QUIT
           EOF