Thread Starter


Hi Guys,

I'm just starting with the whole new world of Modbus and already failing :), so hope you guys can help me.

What I want to achieve is a wireless TCP modbus network. I have started with downloading master and slave software and managed to get this working on one computer (where the slaves listens via to the master).

Step 2 was to create a wired network (via a netgear N600 router) and install the slave software on 1 computer and the master on the other. This was working without any issues. I was able to send registers from the master to the slave over the wired network.

Next step was to remove 1 network cable and connect the notebook (the same from the wired setup) wirelessly to the router and do the same as in step 2). Unfortunately, this failed and I still have no idea why....

I have Googled around too much and cannot find anything. The only thing mentioned there was port forwarding, but since I'm in the same LAN, this should not matter.

Who can gently nudge me in the correct direction? :)

Cheers guys!


What type of devices are at work here? PC's running software? PLC's? Remote I/O Bricks?

Is the slave still hard wired to your router?
Do you have a timeout period or watchdog timer set on either device?
How did you handle the transition from the Wired network to the wireless network? Were the devices reset and allowed to come back up on the new network interface? Is either device still attached to a wired network?
Do you get response to pinging the device over wireless?

There could be other things at play here that come to mind but these first points are where I'd start. Modbus works fine over wireless, but wireless networks have some idiosyncrasies when compared to wired networking and we just have to deal with it. If the slave device has native wireless, then make sure it prioritizes the wireless network and is connected to the AP. Troubleshoot the masters connection to the AP by pinging, then ping the Modbus slave, if it responds then try sending modbus messages. If it fails there try resetting your software and try again. Since it's wireless, any timeout periods you are going to want to extend because of the added latency of the wireless network.
We have same installation to transmit data over 1 km distance for this we have following hardware:

TP link WIFI transmitter

TP Link WIFI Receiver. This devices can be configured as transmitter/receiver or both, like hot spot.

And wired transmitter device with Modbus data source & receiving device at our LAN. this is working ok with any additional settings.