Iterator : any type implementing the iter and next method.Iterable : any type implementing the iter method.Sized : any type implementing the len method.If a type has the methods specified in the protocol, then it implements the protocol. Python does not need explicit protocol declaration. Protocols in Python work a little bit differently. Protocol is both in regular language as well as in Computer Science, probably TCP Protocol, UDP Protocol or also HTTP Protocol. Which is free and best modbus simulator | compiler | Basics of modbus and simulator It has full server control context, a number of backing contexts. It has several asynchronous and synchronous versions, it can read and write protocol on discrete and required register. It is also used without any third party dependencies. Modbus protocol is used for transferring data between programmable logic controller (PLC) and other devices. Modbus is based on master slave concept were master sends request to the slave and slave will respond with the requested message. In other words modbus is used for transmitting information over serial lines between electric devices. Modbus is a serial communication protocol and it is open standard i.e.