B&B Electronics MESR9xx manual TCP Transmission Control Protocol

•For a Class D network (IP addresses 224.0.0.0 through 239.255.255.255) and Class E Networks (IP addresses 240.0.0.0 through 255.255.255.255) the subnet mask is ignored.

•MESR9xxModbus Gateways come from the factory with a default subnet mask value of: 255.255.255.0

TCP (Transmission Control Protocol)

TCP (Transmission Control Protocol) provides reliable connection-oriented network communication with error checking. In TCP mode the Modbus gateway can be configured as a client or a server.

When the Modbus gateway is configured as a TCP client it initiates connections with a server on the network. You must set up the IP address and port number of the server that you want the client (Modbus gateway) to communicate with. You also select whether the Modbus gateway is to connect at power up or only when it receives data from the device connected to its serial port.

When the Modbus gateway is configured as a TCP server it waits for connections to be initiated by another network device. You must set up the TCP port number that it will listen to for connections and set the maximum (up to eight) number of simultaneous connections it will accept. You can filter the connections it will accept based on specific IP addresses or ranges of IP addresses that you specify.