DNS Dialog??
 

If I were to open a connection on port 53 to a name server. What commands would I send to it to resolve host names?

DNS queries are UDP based, so opening up port 53 (like with telnet) will not work. If you are asking about quering a DNS server in code, then take a look at: man resolver

Re: DNS Dialog??
 

you can't really open a "connection" as the UDP protocol is connectionless...

Quote:

What commands would I send to it to resolve host names?

look at "man resolver" as suggested by scowles, or you can also use a packet sniffer when making a dns query...


what do you mean with this?? telnet listens on port 23/tcp and hence uses connections...

dns servers listen on port 53/udp... the port needs to be open and accessible for them to work...

Sorry for the confusion. I did not really understand what the OP was asking (command line or code), so I was referring to using "telnet dns_server 53", which will not work since DNS queries are UDP based.

OK - so it uses UDP and UDP is a conectionless protocol. But how does that work, you send something to the DNS server and it sends a response, but there is no connection. So how does the program querying the DNS server know where to look for it? :confused:

I used telnet as an example, but as it only does TCP connections thats a bit useless. If I were to use socket proramming in C for example. Surely the commands you send to the DNS server are documented somewhere, I can't seem to find them anywhere though.

See: man resolver
See: man gethostbyname

This might be more of a developers forum question, but try these out:

http://www.protocols.com/pbook/tcpip7.htm
http://www.cis.ohio-state.edu/htbin/rfc/rfc1035.html
http://www.cis.ohio-state.edu/htbin/rfc/rfc1706.html

For a tool, the perl sockets module might be a quick start.