Re: How to find out if a TCP port is in use?
Re: How to find out if a TCP port is in use?
- Subject: Re: How to find out if a TCP port is in use?
- From: Julian <email@hidden>
- Date: Fri, 17 Mar 2006 19:16:00 -0300
Hi Stephan!
Here is an example of use:
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>
typedef struct sockaddr *sad; /* A necesary dummy typedef */
#define PORT 80
int main()
{
int sock; /* Socket that will be bind */
struct sockaddr_in sin; /* Address Structure */
/* Create the socket */
/* PF_INET is the option for make a TCP socket.
You can try "man socket" for more info */
sock = socket( PF_INET, SOCK_STREAM, 0 );
/* The socket creation failed */
if ( 0 > sock ) {
perror( "socket" );
return ( -1 );
}
/* Address */
sin.sin_family = AF_INET;
sin.sin_port = htons( PORT ); /* htons() convert the number
to big endian */
sin.sin_addr.s_addr = INADDR_ANY;
/* We bind the socket to the port PORT to check if
the port is in use */
if ( 0 > bind( sock, (sad)&sin, sizeof( sin ) ) ) {
/* Bind failed, now we can check if the address is
in use */
if ( EADDRINUSE == errno ) {
/* We put the code necesary to manage this case */
printf( "The TCP port %d is in use.\n", PORT );
}
else
/* If the error were other than EADDRINUSE, we print it */
perror( "bind" );
}
/* If we arrive to this point, the port weren't in use and
we have it attached to our program. We can close
the socket or use it */
close( sock ); /* Close the socket */
return 0;
}
Note that if you run this program without root privilegies, you can
not check if a port < 1024 is in use.
I hope it can help you. If you have any question about it, please, writeme.
Regards, Julian
On 3/17/06, Finlay Dobbie <email@hidden> wrote:
> On 17/03/06, Stephan Ruggiero <email@hidden> wrote:
> > Hi,
> > thank you, I think this should do the trick.
> >
> > lsof -i :abc
> > gives me every process listening on or connected to the port abc.
> >
> > If other user`s processes are needed, you can just run lsof with sudo.
>
> Well, I wouldn't use this approach if you want to determine this
> programmatically.
>
> -- Finlay
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