Hello engco;

Why are you starting to feel frustration?

First you ask how to connect 2 PLCs of the S7-1200 family. You got some very good answers, from William_B for example, stating that you can use the integrated Ethernet port of the PLCs to do so, possibly with a switch between the two (if ever you would need to add another partner on the network). The Ethernet port supports Profinet natively, so that is the easiest way to connect the PLCs. There is no extra hardware to purchase/configure for this.

Now you ask to connect a PLC (of the S7-1200 family, I presume) with a PC. For programming? SCADA? In any case, the integrated Ethernet port of the PLC can still be used, the PC could have a standard NIC, and you should think of a switch between the two, if you ever plan to have more than these 2 units on the network. There would be no extra hardware required, again

If you need more information please ask for it with a clear and defined question. We will be happy to answer, just as clearly.

Hope this helps,

Daniel Chartier.

I want to connect two plcs or more  to  the computer to make a scada system. and I prefer to do it using Ethernet port not RS224/485. so I need a switch that has RJ ports to be able to connect the all plcs to the computer, is it available ?

Hello engco;

Along with these Compact switches, you will find many industrial switch manuafacturers on the market.

For example, here are a few offerings for unmnanged Ethernet switches generally available in most countries:

Siemens:

http://w3.siemens.com/mcms/industrial-communication/en/ie/industrial-ethernet-switches-media-converters/pages/industrial-ethernet-switches-media-converters.aspx

Belden :

https://belden.com/products/industrialnetworking/unmanagedswitches/

Moxa :

http://www.moxa.com/product/EDS-208205.htm

Red Lion :

http://www.redlion.net/products/industrial-networking/ethernet-solutions/unmanaged-ethernet-switches

Hope this helps,

Daniel Chartier