Added modbus protocol

docs/protocols/modbus.md

@@ -0,0 +1,41 @@
+# Modbus
+
+### Discovery
+
+**Modbus Client:** 
+
+ - [QModBus](https://sourceforge.net/projects/qmodbus/)
+ - [pymodbus](https://github.com/riptideio/pymodbus)
+ - [Modbus Tools](https://www.modbustools.com/) 
+
+**Modbus Discover Nmap Script:**
+
+```bash
+nmap --script modbus-discover.nse --script-args='modbus-discover.aggressive=true' -p 502 <host>
+```
+
+**Connect to Modbus Slave:**
+
+``` python
+from pymodbus.client import ModbusTcpClient
+
+client = ModbusTcpClient('<IP_Address_of_Target>')
+client.write_coil(1, True)
+result = client.read_coils(1,1)
+print(result.bits[0])
+client.close()
+
+```
+
+**Modbus Pentesting:**
+
+ - [smod](https://github.com/0x0mar/smod)
+
+**Modbus Slave Simulator**
+
+ - [Diagslave](https://www.modbusdriver.com/diagslave.html) 
+ - [ModbusPal](https://modbuspal.sourceforge.net/) 
+
+**Modbus Master Simulator**
+
+ - [modpoll](https://www.modbusdriver.com/modpoll.html)