Yaskawa MP920 Communications Module - Manual (Page 292)

Appendix C C Language Sample Programs
C.2.2 UDP (When Using Extended MEMOBUS Protocol)
C-16
// Creates UDP socket.
sd = socket( AF_INET, SOCK_DGRAM, 0 );
if ( sd <= 0 ) // Value 0 or less will be returned if an error occurs in processing.
{
printf( "Error: Socket !!\n" );
exit(0);
}
// Execute a bind to allocate local port number.
rc = bind( sd, ( struct sockaddr *)&my, sizeof(struct sockaddr_in));
if ( rc == -1 ) //
- 1 will be returned if an error occurs in processing.
{
closesocket( sd );
printf( "Error: bind !!\n" );
exit(0);
}
// Immediately waits for receive data since there is no other connection.
// Extended MEMOBUS data sending and receiving processing
// A response must be sent for the received command when using the extended MEMOBUS protocol.
// Repeats receiving the command data and sending the response data.
while(1)
{
// Receives the command data.
// This processing will not end if the Master does not send the command.
fromlen = sizeof(struct sockaddr);
rlen = recvfrom( sd, &rbuf[0], sizeof(rbuf), 0, (struct sockaddr *)&from, &fromlen );
if ( rlen <= 0 )//Value 0 or less will be returned if an error occurs in receiving data.
{
closesocket(sd);
printf( "Error: Recv !! -> %d\n", rlen );
exit(0);
}
// Checks the receive data.
rc = chk_cmd_data( rlen );
if ( rc != 0 ) //Errors in the receive data
{
closesocket(sd);
exit(0);
}
// Prepares the response data.
mk_rsp_data( &send_len );
// Sends the response data.
// This processing will not end if the Slave cannot send the response data.
slen = sendto( sd, &sbuf[0], send_len, 0, (struct sockaddr *)&from, sizeof(struct sockaddr));
if ( slen != send_len ) // The number of bytes that was sent will be returned if the sending processing is
suc-
cessful.
{
closesocket(sd);
printf( "Error: Send !! -> %d\n", slen );
exit(0);
}
printf( "Hit Any Key !!\n" );
}
}