[noob] Connecting to a server using telnet

Brussels Sprout

I started the Web Applications course today on udacity.com. It's quite interesting however I had a problem with one of the exercises that required me to install telnet (I'm using Windows 7).

After installation I tried to connect within the telnet window to the host using the command:

o www.udacity.com 80

and I get a message saying "connecting to www.udacity.com..." which sounds good but unfortunately it stays there forever.
If I try other port numbers (or no port number at all) I get error messages saying that I can't connnect.

Am I doing something wrong here or is this likely to be an issue with the server. (Do I have to wait for it to be vacant or something?)

Also I can't run telnet from the command prompt as windows won't recognise the telnet command. Is this something to do with my environmental variables?

srsly78

Telnet is not secure, you should be using ssh instead.

Annnnyway, try something like "o 1.2.3.4:80" instead.

Install a proper client like putty: http://www.chiark.greenend.org.uk/~sgtatham/putty/

syklops

Works ok for me.

I don't know what telnet client you downloaded, but can I recommend ncat instead. It is very powerful.

Brussels Sprout

syklops wrote: »

Works ok for me.

I don't know what telnet client you downloaded, but can I recommend ncat instead. It is very powerful.

I was directed to go into the Control Panel/Programs menu and then into the "Turn Windows features on or off" menu. From there I checked the box next to Telnet Client and hit ok to install it.

syklops

srsly78 wrote: »

Telnet is not secure, you should be using ssh instead.

Annnnyway, try something like "o 1.2.3.4:80" instead.

Install a proper client like putty: http://www.chiark.greenend.org.uk/~sgtatham/putty/

well he is using port 80, which is HTTP so its as secure as any HTTP website would be. If you try to ssh to a webserver on port 80 it wont work.

OP, it could maybe be a firewall blocking it. If it sees the executable telnet, and goes "oooh, bad telnet", it might be blocking it, despite the fact you just want to use it to talk HTTP to a web server

Colonel Panic

syklops wrote: »

well he is using port 80, which is HTTP so its as secure as any HTTP website would be. If you try to ssh to a webserver on port 80 it wont work.

OP, it could maybe be a firewall blocking it. If it sees the executable telnet, and goes "oooh, bad telnet", it might be blocking it, despite the fact you just want to use it to talk HTTP to a web server

At least someone read the original post!

Brussels Sprout

srsly78 wrote: »

Annnnyway, try something like "o 1.2.3.4:80" instead.

I tried

o 1.2.3.4:80

Could not open connection to host on port 23, Connect failed

o.1.2.3.4 :80

Could not open connection to host on port :80, Connect failed

o.1.2.3.4 80

Connecting To 1.2.3.4.... (but nothing else happens-it neither fails nor connects)

dazberry

The issue is you are connecting to port 80 (HTTP), I'd bet it is connecting fine, but nothing is being echoed back and the server is waiting for you to issue a HTTP request. Try it again and type something and press return and see what happens...

D.

Colonel Panic

That's just an example IP address he provided.

The IP address it maps to is 209.85.142.121 but for reasons I won't go in to, that might not work because many hosts might be sharing the same IP address.

dazberry, I think the problem is he's not connecting at all to let him look at a blank window waiting for a HTTP request to be sent!

Brussels Sprout

syklops wrote: »

OP, it could maybe be a firewall blocking it. If it sees the executable telnet, and goes "oooh, bad telnet", it might be blocking it, despite the fact you just want to use it to talk HTTP to a web server

Would that firewall be on my side or the server side? (apologies if that's a ridiculous question)

Colonel Panic

It would be the firewall on your side. On the server side, it should at least let you connect.

Brussels Sprout

Colonel Panic wrote: »

It would be the firewall on your side. On the server side, it should at least let you connect.

Ok so should I attempt to disable this for telnet or should I just download one of those other programs altogether?

syklops

Brussels Sprout wrote: »

Would that firewall be on my side or the server side? (apologies if that's a ridiculous question)

Your side, as a webserver would not normally block traffic to port 80.

If you run ncat, you should be able to run it in verbose mode(-v or -vv), so it will tell you exactly what is happening.

On my machine when I run nc(similar to ncat), I get:

[syklops@newgrange ~]$ nc www.udacity.com 80 -vv
Connection to www.udacity.com 80 port [tcp/http] succeeded!

I then proceed to try and grab the index page by doing :

GET index.html HTTP/1.1

It says the URL does not exist but at least I get something back from the server so I know it is accepting requests.

dazberry

Colonel Panic wrote: »

dazberry, I think the problem is he's not connecting at all to let him look at a blank window waiting for a HTTP request to be sent!

o www.udacity.com 80

If he's specifying (o)pen, he's running from the (Microsoft) Telnet> prompt, and the screen does not clear when you run it this way and it looks like it has frozen but has connected as it's waiting for a request.

D.

Brussels Sprout

syklops wrote: »

Your side, as a webserver would not normally block traffic to port 80.

If you run ncat,

I installed nmap/ncat and then was able to run ncat from the command line by prefacing the host with the word ncat. Thanks for that.

One more thing. I got back some information from a server but there was so much there (a big webpage) that I couldn't scroll all the way back up to where I had typed my request information. Any idea how to resolve that?

conor.hogan.2

telnet
set logfile telnetlog.txt
o www.udacity.com 80

then:
GET / HTTP/1.0
Host: www.udacity.com

works on Windows.

Putty and telnet in cmd prompt both do not show all results. I am sure there is probably some equivalent to less or more around. Putty seems to just exist on request.

syklops

By connecting to port 80 of a webserver, you are emulating the behaviour of a web browser. What you don't see is that the web browser takes what you have seen and converts the markup tags into more readable text and presents a nice looking(though often not) web page.

Raw markup can be mutiple times larger than the text it needs to display. For example, to print "hello world" in HTML, can take as much as 5-10 lines of markup code.

Thankfully you can redirect the output of netcat to a file using command redirection operators. To do this type

ncat host port > saved_output.txt

In the above example, host is the address you are connecting to and port is the port number(80).

See Using command redirection operators for more information