Issues connecting to Serv-U 4.0 Server with PASV mode

I have seen a number of other posts about problems working with Serv-U.

As you can see I am running 983 - developer version.

What is the problem here, and is there any detailed log I can view that gives me data on why a connection is timing out...

SmartFTP v1.0.983.13
Resolving host name
Resolving host name
Connecting to Proxy ( -> IP: PORT: 21
Connected to Proxy ( -> Time = 0ms
Socket connected waiting for login sequence.
220 (NetCache) Tue, 04 Jan 2005 14:17:19 GMT
331-Serv-U FTP Server v4.0 for WinSock ready...
331 User name okay, need password.
PASS (hidden)
230 User logged in, proceed.
215 UNIX Type: L8
REST 100
350 Restart accepted, proceed with tranfer command.
350 Restart accepted, proceed with tranfer command.
257 "/" is current directory.
200 Type set to A.
227 Entering Passive Mode (10,17,223,33,122,205)
Opening data connection IP: 10,17,223,33,122,205 PORT: 31437.


Eric Volness
BHP Billiton

Hello ...

I tested with other FTP clients and I get exactly the same problem as with SmartFTP. This makes me think it's a problem with the server or the server software (serv-u 4.x). PORT mode works on the server you did the tests on. To change from PASV mode to PORT mode, go to Menu: Tools->Settings->Connection "Data Connection".



It is good to confirm that PORT mode works from elsewhere. Unfortunately we can only accept PASV mode.

Is there some way to diagnose the PASV mode messages?

Where can I find a verbose listing of what is happening within smartFTP?

Hello ...

There are no detailed information regarding the problem/error. SmartFTP tries to open a connection to the IP,Port specified in the PASV reply from the server and it never gets a onconnection() socket event.
The problem is as said before with the FTP server and not with the FTP software. Serv-U 4 has several bugs which have been adressed in future versions. The latest Serv-U version is 6.0. See the changelog at:


I tend to agree with mb. The only thing that makes we wonder is that somtimes I get a "port not specified" error. But I think that is coming from the server.

Funny thing is that with passive mode through a proxy sometimes it works and sometimes not. Some servers it seems to work better on.

530 PASV command only accepts connection from client IP address (155.***.***.***!=error).
550 List failed. No port specified.

In this case though it seems that the client is sending a request to the server to open a data connection and is not specifying a port. So that would either have to be Smarts fault or the Proxy servers fault.

But then again on mircosofts anonomous ftp site it seems to work fine:

250 CWD command successful.


257 "/deskapps/excel/KB" is current directory.


227 Entering Passive Mode (207,46,133,140,62,112).

    Opening data connection IP: 207,46,133,140,62,112 PORT: 15984.

    LIST -aL

125 Data connection already open; Transfer starting.

    72 bytes received successfully. (72 B/s) (00:00:01).

226 Transfer complete.

The difference is where it says data connection already open.........

Files Are Not Posted Using FTP "PUT" Command through Microsoft SOCKS Proxy Service
Article ID : 233285
Last Review : October 16, 2002
Revision : 1.0
This article was previously published under Q233285
On this Page
When you attempt to use the FTP "PUT" command using a SOCKS 4-compliant FTP client through Microsoft SOCKS Proxy Server service, the file is not successfully posted to the FTP server. There are no errors associated with this symptom, except that the file does not exist after uploading.
This problem is due to the SOCKS server always performing a hard reset on the Internet socket closure in order to save time. This, in turn, causes the FTP server to reset during the PUT command.
To resolve this problem, obtain Microsoft Proxy Server 2.0 Service Pack 1. For additional information about Service Pack 1, please see the following article in the Microsoft Knowledge Base:
238375 Proxy Server 2.0 Service Pack 1: List of Fixes
Microsoft has confirmed that this is a problem in Proxy Server 2.0.