8 Network CommunicationThe block library can be found for download in the ‘Service/Support’ area ofwww.vipa.com at ‘Downloads è VIPA Lib’ as ‘Block library Network Communication -SW90FS0MA’ . The library is available as packed zip file. As soon as you want to usethese blocks you have to import them into your project.Ä Chap. 5 ‘Include VIPA library’page 698.1 Open Communication8.1.1 Connection-oriented protocolsn Connection-oriented protocols establish a (logical) connection to the communicationpartner before data transmission is started. And if necessary they terminate the con-nection after the data transfer was finished.n Connection-oriented protocols are used for data transmission when reliable, guaran-teed delivery is of particular importance. Also the correct order of the receivedpackets is ensured.n In general, many logical connections can exist on one physical line.n The following connection-oriented protocols are supported with FBs for open commu-nication via industrial Ethernet:– TCP/IP native according to RFC 793 (connection types 01h and 11h)– ISO on TCP according to RFC 1006 connection type 12h)n During data transmission, no information about the length or about the start and endof a message is transmitted. However, the receiver has no means of detecting whereone message ends in the data stream and the next one begins.n The transfer is stream-oriented. For this reason, it is recommended that the datalength of the FBs is identical for the sending and receiving station.n If the number of received data does not fit to the preset length you either will get notthe whole data, or you will get data of the following job.n The receive block copies as many bytes into the receive area as you have specifiedas length. After this, it will set NDR to TRUE and write RCVD_LEN with the value ofLEN. With each additional call, you will thus receive another block of sent data.n During data transmission, information on the length and the end of the message isalso transmitted. The transfer is block-orientedn If you have specified the length of the data to be received greater than the length ofthe data to be sent, the receive block will copy the received data completely into thereceive range. After this, it will set NDR to TRUE and write RCVD_LEN with thelength of the sent data.n If you have specified the length of the data to be received less than the length of thesent data, the receive block will not copy any data into the receive range but insteadwill supply the following error information: ERROR = 1, STATUS = 8088h.8.1.2 Connection-less protocolsThere is thus no establishment and termination of a connection with a remote partner.Connection-less protocols transmit data with no acknowledge and with no reliable guar-anteed delivery to the remote partner. The following connection-oriented protocol is sup-ported with FBs for open communication via Industrial Ethernet:n UDP according to RFC 768 (with connection type 13h)Block library "NetworkCommunication"TCP nativeISO on TCPVIPA SPEED7Network CommunicationOpen Communication > Connection-less protocolsHB00 | OPL_SP7 | Operation list | en | 18-30114
