Last year, we started to exchange 2g/3g modems for Teltonika TRB140 4g. We use the modems to connect to remote locations directly, and in some of those locations, we have devices with integrated FTP servers. Before the upgrade to Teltonika TRB140, we didn’t have any problems connecting to FTP servers with FileZilla. Now, when trying to connect, we get “Connection established, waiting for welcome message…” and “421 Service not available, closing control connection.”. Sometimes it stops at listing directories.
Our network consists of multiple 4G modes with SIM cards; each modem has a static IP. We connect to the mobile network via an IPSec VPN tunnel.
We port forwarded to ports 21 and 20, and still it doesn’t work. The old modem had the same settings.
I understand you previously used 2G/3G modems that have now been replaced by the TRB140 gateway. Could you please explain how they were set up before? Also, where is the IPSec tunnel client running? Is it on the TRB140 or on another instance? Additionally, could you clarify the network topology, specifically how your FTP server is connected—whether it’s connected directly to the TRB140 or to another 2G/3G modem?
They were set up the same way as the new TRB140 gateway.
We enter our APN information and port forward, and that’s it.
Some of those 2G/3G modems were from Teltonika (I don’t know which model). The IPSec VPN tunnel is set up in our office using a Mikrotik router. The tunnel goes from our office to our mobile network provider.
On our network, nothing was changed except for the new 4G gateway on site.
In this particular case, the FTP server is integrated into the SMA Webbox (a solar power plant monitoring device). The SMA Webbox is directly connected to the TRB140 gateway. I can access the SMA Webbox GUI and Teltonika GUI remotely without a problem.
If you’re used to using modems, a gateway is quite different. A modem connects your home network to your internet service provider (ISP) by converting digital data from your network into signals that can travel over your ISP’s infrastructure (usually DSL, cable, fiber, or satellite).
On the other hand, a gateway combines the functions of a modem and a router into a single device. It not only connects your home network to the internet but also manages traffic between devices on your network. This includes providing features such as Wi-Fi access, firewall protection, and network management.
To ensure that your other devices, like MikroTik routers, maintain their configurations, consider putting the TRB140 into passthrough mode. This will allow it to function like a standard 2G/3G modem.
Here’s how to do it:
Navigate to Network → WAN and click “edit” next to the mobile interface.
In the pop-up window, set the mode to “Passthrough.”
By doing this, the TRB140 will operate simply as a modem.
Connection established, waiting for welcome message…
Status: Insecure server, it does not support FTP over TLS.
Status: Server does not support non-ASCII characters.
Status: Logged in
Status: Retrieving directory listing…
Command: PWD
Response: 257 “/”.
Command: TYPE I
Response: 200 Command okay.
Command: PASV
Response: 227 Entering Passive Mode (192,168,0,168,17,188).
Command: LIST
Error: Connection timed out after 20 seconds of inactivity
Error: Failed to retrieve directory listing