# OPAL-RT {#opal} The communication between OPAL-RT models and the S2SS is established by using ansychronous programs. Asynchronous programs are are a feature of RT-LAB. They are used to exchange data between Simulink models and custom C programs. For this purpose the C program handels IP/UDP communication via BSD sockets. ## Arguments for OPAL-RT block RT-LAB already provides a block to establish simple TCP/IP communication: ??? This block is based on a more generic block used for aynchronous programs: ??? @todo Insert name of RT-LAB blocks. | Param | Description | Example Value | | :------------- | :------------ |:-------------- | | FloatParam[0] | Protocol | | | FloatParam[1] | RemotePort | 10200 | | FloatParam[2] | LocalPort | 10201 | | StringParam[0] | RemoteAddr | 192.168.0.10 | | StringParam[1] | LocalAddr | 192.168.0.11 | | StringParam[2] | InterfaceName | eth2 | @todo Complete documentation for the OPAL-RT Simulink module.