ex_tcp_echo.c

This example program shows how to send and receive TCP data. This program acts as the server, and listens for any data entering on TCP port 54123. If a TCP message is received, we read it and return data to the same socket (IP and port) that just sent us data. It implements a circular buffer for storing the received data.

#include "net\tcp.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 tcpRxBuf[256];
#pragma udata   //Return to default section

//Get and Put pointer for tcpRxBuf circular buffer. If Get pointer = Put
//pointer, the buffer is empty.
BYTE tcpRxBufGet, tcpRxBufPut;

//Create a TCP socket for receiving and sending data
static TCP_SOCKET tcpSocketUser = INVALID_SOCKET;


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

    //Set TCP Receive buffer to be empty
    tcpRxBufGet = tcpRxBufPut = 0;

    //Configure to listen on port 54123
    tcpSocketUser = TCPListen(54123);
    
    //An error occurred during the TCPListen() function
    if (tcpSocketUser == INVALID_SOCKET) {
        //Take any additional action that is required when an error occurs
    }

    //Infinite loop. Check if anything is received on TCP port
    while(1)
    {
        //Has a remote node made connection with the port we are listening on
        if (TCPIsConnected(tcpSocketUser)) {
            //Is there any data waiting for us on the TCP 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 (TCPIsGetReady(tcpSocketUser)) {

                //Read all data from socket, and save it to TCP Receive buffer (tcpRxBuf)
                while(TCPGet(tcpSocketUser, &c)) {
                    //Store byte read from TCP socket to TCP buffer
                    tcpRxBuf[tcpRxBufPut++] = c;
            
                    //If Put pointer caught up to Get pointer, our buffer is full and we have
                    //lost data!
                    //Increment Get pointer.
                    if (tcpRxBufPut == tcpRxBufGet) {
                        tcpRxBufGet++;
                    }
                }

                //Discard the socket buffer.
                TCPDiscard(tcpSocketUser);
            }


            //Does the TCP receive buffer contain any data? If so, we sent this data back
            //to the same socket that just send us data. 
            if(tcpRxBufPut != tcpRxBufGet) {
                //Checks if there is a transmit buffer ready for accepting data, and that
                //the given socket is valid (not equal to INVALID_SOCKET for example)
                if (TCPIsPutReady(tcpSocketUser)) {
            
                    //Transmit entire buffer
                    while (tcpRxBufGet != tcpRxBufPut) {
                        TCPPut(tcpSocketUser, tcpRxBuf[tcpRxBufGet++]);
                    }

                    // Now transmit it.
                    TCPFlush(tcpSocketUser);
                }
            }
        }


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