FTP Server disconnecting users...

[Jeff7181]

I can't figure this out... my connection is very high quality... never have any problems with it. But I've tried setting up an FTP server many times and users always get disconnected before a file transfer finishes. I've tried it on different ports as well with no luck. I've used IIS and GuildFTPd and get the same problems. Could the cable company be monitoring the line and when it see's "FTP like" activity for a certain period of time it closes that connection?

 

[Scarpozzi]

FTP is a very light-weight protocol. I highly doubt the cable company would do that. However, you should be aware that there are 2 kinds of FTP servers: Active and Passive. I know some of the passive FTP activity could be confusing to a network engineer since it hits so many incremented ports. It almost appears to be a port scan if you get enough traffic in a short period of time. If you have the configuration options to lock down the ftp server and make it stay less than port 1024 rather than incrementing, they will probably leave you alone.

-Scar

 

[Jeff7181]

Originally posted by: Scarpozzi
FTP is a very light-weight protocol. I highly doubt the cable company would do that. However, you should be aware that there are 2 kinds of FTP servers: Active and Passive. I know some of the passive FTP activity could be confusing to a network engineer since it hits so many incremented ports. It almost appears to be a port scan if you get enough traffic in a short period of time. If you have the configuration options to lock down the ftp server and make it stay less than port 1024 rather than incrementing, they will probably leave you alone.

-Scar

So even if I tell it to use port 21 that's not enough?

 

[Fuzznuts]

no port 21 is used for connection the listing is then sent over port 20 by default. to make a full stream connection if 20 is closed it will choose a port < 1024 t o connect the remote client to and then send data that way.
problems occur when you have firewalled those ports or your ftp is behind nat as it will try to attach to an internal ip unless you have done special settings to do fool it.

most ftp servers will allow you to specify a passive port range set it over 1024 and say a rnage of 100 ports. then allow those ports in your firewall.

however it sounds like your getting the inital connection fine but it fails later on if that is the case ports and passive changes wont help you. in whcih case id be looking at timings and filesizes.

does the dropout occur in the same time frame ie very 10mins every hour etc also does it choke on large files or high speeds?

loads of factors to look into unfortunately