get the remote port number

HarryBoy · 06-06-2012, 06:23 AM

I have a c++ cgi script that gets called and I get the IP address of the client like so:

Code:

char* remote_host = getenv("REMOTE_ADDR");

But I need to get the remote client port numer as well. I believe that APACHE doesn't set the REMOTE_PORT so can I get it using sin_port or anyting??

How can I do this???

Thanks

NevemTeve · 06-06-2012, 09:07 AM

Try getpeername(fd=0/1).

Nominal Animal · 06-06-2012, 09:29 AM

The CGI program is typically not directly connected to the client socket in any way, so getpeername() is unlikely to work. The correct solution is to tell Apache to provide the REMOTE_PORT environment variable for you.

The simplest method I can think of is to enable URL rewriting via the mod_rewrite module: add

Code:

RewriteEngine  On
Options        +FollowSymlinks
RewriteCond    (%{REMOTE_PORT}) ^
RewriteRule    ^ - [E=REMOTE_PORT:%1]

to the Directory section that governs your CGI scripts in your Apache configuration.

The way this works is that the URL rewriting engine knows about the remote port; it refers to it as %{REMOTE_PORT}. Since it is in parentheses, it will be accessible in any applied rule using %1. Since every string has a start, the condition always matches. The rule always matches also. The - tells the rule to do no replacements. The [E=REMOTE_PORT:%1] sets the REMOTE_PORT environment variable as per the remote port. For the rewrite engine to work, both RewriteEngine and symlinks (FollowSymlinks or SymlinksIfOwnerMatch) must be enabled.