FTP server Issue -sometime getting "Not logged in message"

Hi,

We are trying to connect to FTP server powered by XFB gateway. We have a client program that keep polling to this server for files. The program work fine with other FTP servers without any problem.

we will login to the server when the client program tries to poll in and get the files and some process will happen.

We can see some 100 login are successful and could see we get the error once in a while and the client is not able to connect until some time (may be 10 mts)
Error occured while FTP login : Not logged in The host is xxx.yyy.in The port used is 6370

This is not happening with any other FT server.

Following is our ftp stat
ftp> stat Connected to server. No proxy connection. Mode: stream; Type: ascii; Form: non-print; Structure: file Verbose: on; Bell: off; Prompting: on; Globbing: on Store unique: off; Receive unique: off Case: off; CR stripping: on Ntrans: off Nmap: off Hash mark printing: off; Use of PORT cmds: on Tick counter printing: off

We are able to connect to the FTP server thru FTP client software without any problem.

But through our client program we get this error often only to that FTP server powered by XFB gateway.

Is it like the FTP server accepts only some connections at a time, if yes how will I set that max time/ session/connections in the server powered by the XFB gateway?

Please help as am struck with this.

Thanks in advance,
Sridevi