ex_udp_echo2.c

This example program shows how to send and receive UDP datagrams with the UDPGetArray() and UDPPutArray() functions. This program acts as the server, and listens for any data entering on UDP port 54123. If a UDP message is received, is is read and sent back to port 54124 of the node that just send us the message.

#include "net\udp.h"

//The following code is for the Microchip MPLAB C18 compiler. For the
//Hi-Tech compiler, the #pragma's are not required
#pragma udata BUFFER1_256BYTES
BYTE udpRxBuf[256];
#pragma udata   //Return to default section

//Remember number of bytes received from the UDP socket
BYTE udpBytesReceived;

//Create a UDP socket for receiving and one for transmitting
static UDP_SOCKET udpSocketUserRx = INVALID_UDP_SOCKET;
static UDP_SOCKET udpSocketUserTx = INVALID_UDP_SOCKET;


void main(void)
{
    BYTE c;
    NODE_INFO udpServerNode;

    //Initialize remote IP and MAC address of udpServerNode with 0, seeing that
    //we don't know them for the node that will send us an UDP message. The first
    //time a message is received addressed to this port, the remote IP and MAC
    //addresses are automatically updated with the addresses of the remote node.
    memclr(&udpServerNode, sizeof(udpServerNode));

    //Configure for local port 54123 and remote port INVALID_UDP_PORT. This opens
    //the socket to listed on the given port.
    udpSocketUserRx = UDPOpen(54123, &udpServerNode, INVALID_UDP_PORT);
    
    //An error occurred during the UDPOpen() function
    if (udpSocketUserRx == INVALID_UDP_SOCKET) {
        //Take any additional action that is required when an error occurs
    }

    //Infinite loop. Check if anything is received on UDP port
    while(1)
    {
        //Is there any data waiting for us on the UDP socket?
        //Because of the design of the Modtronix TCP/IP stack we have to consume
        //all data sent to us as soon as we detect it. Store all data to a buffer
        //as soon as it is detected
        if (UDPIsGetReady(udpSocketUserRx)) {

            udpBytesReceived = UDPGetArray(udpRxBuf, 256);
        
            //Discard the socket buffer.
            UDPDiscard();

            //Check if the UDP socket for transmitting has been created yet. We
            //only create this socket after we have received a UDP datagram from
            //the client. The reason is that we use the IP and MAC address
            //from the received UDP datagram
            if (udpSocketUserTx == INVALID_UDP_SOCKET) {
                //Create UDP socket for sending data to remote client on port 54124.
                //We use the UDPGetNodeInfo() go get the IP and MAC address of the
                //remote client. Configure for local port 54130 and remote port 54124.
                udpSocketUserTx = UDPOpen((WORD)54130, UDPGetNodeInfo(), (WORD)54124);
    
                //An error occurred during the UDPOpen() function
                if (udpSocketUserTx == INVALID_UDP_SOCKET) {
                    //Take any additional action that is required when an error occurs
                }
            }
        }


        //Does the UDP receive buffer contain any data?
        if(udpBytesReceived > 0) {
            //Checks if there is a transmit buffer ready for accepting data, and
            //that the given socket is valid (not equal to INVALID_UDP_SOCKET for example)
            if (UDPIsPutReady(udpSocketUserTx)) {
            
                //Send all bytes received
                UDPPutArray(udpRxBuf, udpBytesReceived);

                udpBytesReceived = 0;  //Indicate all bytes have been sent
            
                // Now send it.
                UDPFlush();
            }
        }

        //This task performs normal stack task including checking for incoming packet,
        //type of packet and calling appropriate stack entity to process it.
        StackTask();
    }
}