How to get the ip address of the client machine

vijirin · 01-02-2011, 10:18 AM

Dear all,

I am connecting to linux server(RHEL4.7) using putty from my windows machine. Is there any way to get the ip address of my windows machine using C program in linux.

Thanks in advance.

Viji

paulsm4 · 01-02-2011, 11:44 AM

Hi -

You can probably just parse the value of $SSH_CLIENT (or $SSH_CONNECTION ).

vijirin · 01-02-2011, 10:00 PM

Hi,

Thanks a lot.

If I am connecting using ssh, it works perfect.

But if i try to connect using telnet, it will not work.

Is there any other way to get the ip?

Regards

Viji

frankbell · 01-02-2011, 10:18 PM

A ping name would normally return the ip address.

an15wn · 01-03-2011, 12:00 AM

Quote:

Originally Posted by vijirin

But if i try to connect using telnet, it will not work.

Is there any other way to get the ip?

I think you can extract the output of who -m command. The ip address of the login terminal is provided there...

vijirin · 01-03-2011, 11:40 AM

Hi,

Is there any system calls to get the ip of the machine?

regards

viji.R

acid_kewpie · 01-03-2011, 02:20 PM

Well you can look at the connection table, e.g. netstat -plnt but system calls seem odd as you are not internal to the server side process itself. What information would you expect to give to this system call? What if you have 100 concurrent connections from 65 different clients?

frankbell · 01-03-2011, 08:31 PM

Quote:

Originally Posted by vijirin

I am connecting to linux server(RHEL4.7) using putty from my windows machine. Is there any way to get the ip address of my windows machine using C program in linux.

I just looked back at your original post. I'm confused.

This is what I'm envisioning after rereading the OP:

Windows with putty-------------ssh>>----------------->Linux
Machine<-------------<<ping--------------------------Machine

You say that you are connecting to the Linux box FROM the Windows machine via putty and want the ip address of the Windows machine that you are sshing FROM, since that's the only Windows machine in the story.

If you want the ip address of your Windows machine, ssh won't help you. Open a command window on the Windows windows machine and run the command ipconfig /all. That's IPconfig, not IFconfig. That will tell you the ip address and the gateway and lots of other stuff for the Windows machine.

From your ssh connection, you could try telling the Linux box to ping back at your Windows box and see what happens.

You could try a traceroute from your local Windows box to the remote Linux box to see how many hops are involved.

If your Windows machine is on a subnet, say a work machine, behind multiple routers, you are unlikely to find out a route from the Big Wide World to your Windows machine. You can use your ssh connection to tell your Linux machine to ping the Windows machine and see what happens. Unless port forwarding is properly set up, though, you won't be able to get to it. If your work IT department is worth their salt, you should not be able to ping your local work Windows machine from outside.

Please let me know whether my re-interpretation of your original request is accurate or wildly off the mark.

If you are trying to telnet into your Linux box, does it have a telnet daemon running?

http://aplawrence.com/Linux/enable_telnet.html

an15wn · 01-03-2011, 09:26 PM

Quote:

Originally Posted by vijirin

Hi,

Is there any system calls to get the ip of the machine?

regards

viji.R

IP address of WHICH machine? Windows?
Where is your application? Linux?

As I suggested before... use the output of who -m.

Simple but needs to process the content of ./guest_ip further.

Code:

system ("who -m > ./guest_ip");

More complex but hopefully no more process needed. Just read the ./guest_ip file.

Code:

system ("who -m | sed  \"s/[^(]*(\([^)]*\))/\1/\" > ./guest_ip");

(untested using C, but the command was tested at the terminal)

This is the scenario:
Machine with ip 10.20.18.51 connect TO 10.20.18.101 via ssh.
The virtual-server ip addr is 10.20.18.101.

Code:

[anis@anis ~]$ ssh 10.20.18.101
anis@10.20.18.101's password: 
Last login: Tue Jan  4 09:23:45 2011 from 10.20.18.51
[anis@virtual-server Sims]$ ifconfig eth5
eth5      Link encap:Ethernet  HWaddr 08:00:27:7F:C2:B2  
          inet addr:10.20.18.101  Bcast:10.20.18.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe7f:c2b2/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8772 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4887 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:759806 (741.9 KiB)  TX bytes:658985 (643.5 KiB)

[anis@virtual-server Sims]$ who -m 
anis     pts/0        2011-01-04 09:23 (10.20.18.51)
[anis@virtual-server Sims]$ who -m | sed  "s/[^(]*(\([^)]*\))/\1/"
10.20.18.51
[anis@virtual-server Sims]$

Good luck...

jcookeman · 01-26-2011, 07:22 AM

This is quite easy to do. However, I would recommend not doing this in C as you will need to mess with Linux specific stuff like the /proc directory. Unless you have good reason doing so, you will save yourself immense maintenance and code writing by using Shell commands as `lsof` or `netstat`.

This is from Linux:

Code:

$ lsof -i tcp:22
COMMAND  PID  USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
ssh     2783 jcook    3u  IPv6 125833      0t0  TCP eli:50512->eli:ssh (ESTABLISHED)

This is from Mac:

Code:

$ lsof -p $PPID -i tcp:22 | grep :ssh-\> | tail -n1 | awk '{print $9}' | awk -F-\> '{print $2}'
eli.config:43187

So, you can see with a little Bash foo you can get exactly what you want, it will be more resistant to change, and can be quite a bit easier on different platforms -- that support Bash of course. The Mac portion is printing out the host name of the client machine (what you want) and the port it has connected to from.