Problem with ftp_get_nlist()

[aschone]

Re: Problem with ftp_get_nlist()

Port 21 is the default command port. FTP is different than typical internet protocols in that it uses both a command port and a data port. Both command and data ports need to be configured to allow access. It would be beneficial to determine what data ports are available to be used by the FTP connection and then determine if the ports on the firewalls and routers are configured properly. Since you are unable to get a log from the A5 side of the ftp communication, I would suggest getting the log information from the server side. This will help in your troubleshooting tremendously. Currently all anyone is able to do is take guesses at what the issue is.

For some reason some firewalls and routers like to play havoc with FTP packets. "Smart" firewalls and routers will sometimes modify the FTP packets and insert different IP addresses for return communications. This might explain why one ISP works and the other doesn't. Other ISP's don't like to allow FTP on the default ports and will block it.

Get the logs from your successful and failed attempts. This will lead us to better troubleshooting than wild guesses in the dark. I am only able to point at the most common issues I run into when supporting my FTP server.

[michaelklein]

Re: Problem with ftp_get_nlist()

This particular FTP server uses standard port 21. As for active or passive mode, how do I configure Alpha5's FTP functions to use one or the other? Since I don't have any problem accessing the FTP site using FileZilla, an FTP client, it would appear that something in the ftp_get_nlist() function is the problem.
--Michael

[aschone]

Re: Problem with ftp_get_nlist()

Sorry for the delay, been out of the office for past couple of days.

I agree, it would be great if we had logging capability of the Alpha5 FTP session.

I am speculating still that it is a network configuration issue with allowed ports coming in and out of the network. It will be beneficial to you to to contact the FTP server admin and determine the supported method of connection, either Active or Passive. Then determine the supported ports. Once you have obtained the Connection type and the list of possible ports you can properly configure your routers and firewalls.

I believe you were able to get a listing once because the FTP server/client port walked you onto an available port that was open.

[michaelklein]

Re: Problem with ftp_get_nlist()

Thanks Cal. I've used MoveITFreely for command-line FTP uploading and downloading. It's worked fine in the past and even supports FTPS protocol. Unfortunately, it appears to have been purchased by Ipswitch and is no longer free :(. If I need another command-line client, I'll definitely check out WCL_FTP.exe. In the meantime, wouldn't it be great if there was a way to debug Alpha5's FTP functions? Anybody from Alpha5 listening ;)?
--Michael

[CALocklin]

Re: Problem with ftp_get_nlist()

FWIW, I've had similar problems with A5's FTP commands in v8 and v9. (Haven't tried them on v10 yet.) On some customer's machines they work fine and on others I can't get them to work even though the application is exactly the same on all machines.

My solution for uploading and downloading files was WCL_FTP.exe which is a freeware ftp command line program. I actually prefer it to using A5's upload/download commands with large files because my xbasic script calls it then it runs in a completely separate window and users can get right back to work in A5 while the file is being transferred - and, most important of all, it works perfectly every time on every machine.

Unfortunately, I haven't found a solution for the ftp "list" functions. I hope someone here comes up with one.

[michaelklein]

Re: Problem with ftp_get_nlist()

I have successfully connected both Active and Passive using the FTP client. During some testing this evening on the non-responsive machine, I was able to get a listing one time. However, subsequent attempts were unsuccessful. As for differences in Wireshark, I don't currently have access to the working session as it's in FL and I'm in NY. I tried to compare sessions from Alpha5 vs. FileZilla FTP client. I spotted 1 slight difference:

When the FTP client disconnects, there is no QUIT command issued while Alpha5 issues a QUIT command. I'm stumped :(.
--Michael

[aschone]

Re: Problem with ftp_get_nlist()

Are you connecting using Passive FTP or Active FTP?

When you monitored the FTP session using Wireshark did you notice any difference between the working session and the non-working session? If not, then did you notice the file listing returned by the FTP server during the non-working session?

[michaelklein]

Re: Problem with ftp_get_nlist()

Andrew,
Thanks for the reply. Unfortunately, multiple FTP clients work just fine on the non-working machine. They connect to the folder in question using the same username and PW as the ftp_get_nlist() and display all of the .jpg files. Any other ideas?
--Michael

[aschone]

Re: Problem with ftp_get_nlist()

Hard to say without error messages or more details. Very possible your ISP is playing havoc on the FTP session. Or possible your firewall or router is the cause.

I would first test by using a basic FTP client. Configure the client both on the working machine and the non-working machine. IF the basic FTP client bombs on the non-working machine you should have logs of the activity helping lead you to the point of the issue.

I would surmise that it is a badly configured router or firewall.

[michaelklein]

This is a weird problem I could really use some help with. I'm trying to populate a drop-down control with the names of picture files located on an FTP site. I have the following code in the OnInit event of a form:

Dim artwork_list as C

artwork_list = ftp_get_nlist("ftp.xxx.com", "validusername", "validPW", "/Pix/*.jpg")

On my desktop machine, when I run the code in the Interactive window, it executes but doesn't return any file names. When I do the same on my laptop using a different ISP, it returns 5 file names. I have even disabled the Windows Firewall, but that didn't help. I've used Wireshark to monitor the FTP conversation and everything seems fine. Does anyone have any idea what could be happening and how I might fix it?
Thanks in advance.
Michael