Duplicated FTP server services on same machine

Recently I had call from customer with very interesting problem. They reported that they can’t connect to dedicated FTP server, either from LAN or from Internet.

This was very strange, as this server working for years without problem. At first, I suggested customer to check Internet link, router and similar settings. When they called me back, I recognized that I must to try myself. Now this sounds like anomaly.

Troubleshooting steps

I logged to FTP server without problem from Internet Explorer. This login is anonymous and passed just like that. But then customer reported that there is no such account on FTP server. As FileZilla FTP server needs even such account, this is definitely anomaly in system.

I asked for FTP account details so that I can check this issue further. I used FileZilla FTP portable client, as troubleshooting tool. FileZilla client shows raw session log, with all messages exchanged between client and server.

I entered credentials and tried to connect. Login failed and session log contained this:

Status:      Connecting to 203.0.113.138 …
Status:      Connected with 203.0.113.138. Waiting for welcome message…
Response:    220 Microsoft FTP Service
Command:     USER User01
Response:    331 Password required for User01.
Command:     PASS ***********
Response:    530 User User01 cannot log in.
Error:       Unable to connect!

I spotted error line and error code above it: 530 User User01 cannot log in.

This error means that username or password is wrong. I made quick search over Internet and found that there were similar problems with other users. However, response point me to the solution.

Actually, third line claims that there is 220 Microsoft FTP Service. But we using FileZilla FTP server. So, something is very wrong here.

I accessed to FTP server over Remote Desktop. On my surprise, I found that there is whole IIS suite, with IIS, FTP and SMTP services.

Solution

Solution was simple. I stopped FTP service. To prevent that someone start service and block FileZilla server again, I changed service port for FTP to 2021. Now, even if someone try to run it again, it will not works on port 21.

I made new test and voila! Our FTP server is back again. Our log now contains following lines:

Status:      Connecting to 203.0.113.138 …
Status:      Connected with 203.0.113.138. Waiting for welcome message…
Response:    220-Welcome to the
Response:    220- Company FTP Server
Response:    220-
Response:    220-All connections will be monitored.
Response:    220-
Response:    220-Illegal access to this server is forbidden.
Response:    220-Any attempt to hack this system will be
Response:    220-prosecuted to the maximum
Response:    220 penalty described in the law.

Command:     USER User01
Response:    331 Password required for user01
Command:     PASS ***********
Response:    230 Logged on
Command:     SYST
Response:    215 UNIX emulated by FileZilla
Command:     FEAT
Response:    211-Features:
Response:     MDTM
Response:     REST STREAM
Response:     SIZE
Response:     MLST type;size;modify*;
Response:     MLSD
Response:     AUTH SSL
Response:     AUTH TLS
Response:     PROT
Response:     PBSZ
Response:     UTF8
Response:     CLNT
Response:     MFMT
Response:    211 End
Status:      Connected
Status:      Retrieving directory listing…
Command:     PWD
Response:    257 “/” is current directory.
Command:     TYPE A
Response:    0 Type set to A
Command:     PASV
Response:    227 Entering Passive Mode (203,0,113,138,15,186)
Command:     LIST
Response:    150 Opening data channel for directory listing of “/”
Response:    226 Successfully transferred “/”
Status:      Directory listing successful
Command:     PWD
Response:    257 “/” is current directory.

Now all FTP users can access server. Case closed! Smile

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3 thoughts on “Duplicated FTP server services on same machine

    • Someone installed IIS suite without reason. Not sure why. However, this is so common user (admin) error.

      A FTP service from IIS started first and took a command port 21 TCP for itself. Therefore, Filezilla server failed to run.

      Like

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