Hi,
I have run into a little problem and was hoping someone could assist me.

I have installed an FTPDaemon on a remote machine but I can only have 5 simultaneous FXP transfers at any given time on account that there is a firewall (I believe) and I was only able to find a small range of open ports (8000-8005) for PASV. The method I used to find them was very tedious. Basically I tried login into the machine though FlashFXP on random ports, if I received a Connection Refused, then I figured I could use that port, but if I timed-out, than that port was unusable.

So my question is, is there an easier/faster method of finding a range of un-blocked ports?
Thanks in advance

This issue has come up quite a few times, and I think I'll eventually get around to coding some kind of app that tests each port, prehaps by using the less restricted UDP protocol as a communication ground between the two programs.
If anyone else has any other methods though, would save me some time..

I posted this on another thread just a few minutes ago, for that I am sorry.

Load up a packet sniffer. If all you have is a shell then tcp-dump will work fine. Then do a vanilla scan form a remote location. There firewall might get pissed off, possably black hole your ass. Since you don't need to know what ports are open, you are just testing there firewall. You can use this nice little program:
http://gps.sourceforge.net/

peace out.

If you try Nmap you can check if a port is filtered or closed...

I thought that when it was filtered you could access it and when it was closed you can't use it at all...

@AgentOrange: Thanks for your reply. Your method sounded promising so I tried it. I installed Windump on the remote host and did a vanilla scan from a remote location. I had Windump output to a txt file and after about an hour I ended up with a 6MB.txt file.

Trying to make sense out of it is confusing, here's just a couple of lines from the output file that Windump generated:

07:00:14.496567 IP my.remote.scanner.com.57512 > my.target.host.8084: S 188111309:188111309(0) win 16384 <mss 1380,nop,nop,sackOK> (DF)

08:19:19.441986 IP my.remote.scanner.com.8500 > my.target.host.19438: S 3144562016:3144562016(0) win 16384 <mss 1380,nop,nop,sackOK> (DF)

To me, those two lines look identical except for the ports. The only difference is that when I try to login into port 8084 with FlashFXP I get a Connection Refused and when I try to connect to 19438, I get timed-out.

@Voxell: I tried Nmap a couple of days ago on a small range of ports that I knew had a few usuable ports. Nmap just stated that they were all filtered so that didn't help me out much.