sp_sendmsg

This sample C program listens on a port that you specify and echoes the messages it receives. For example, to receive the sp_sendmsg calls for Example 1, use:

updmon 3456
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>

main(argc, argv)
int argc; char *argv[];
{
        struct sockaddr_in sadr;
        int portnum,sck,dummy,msglen;
        char msg[256];

        if (argc < 2) {
                printf(“Usage: udpmon <udp portnum>\n”);
                exit(1);
        }

        if ((portnum=atoi(argv[1])) < 1) {
                printf("Invalid udp portnum\n");
                exit(1);
        }

        if ((sck=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP)) < 0) {
                printf("Couldn't create socket\n");
                exit(1);
        }

        sadr.sin_family = AF_INET;
        sadr.sin_addr.s_addr = inet_addr("0.0.0.0");
        sadr.sin_port = portnum;

        if (bind(sck,&sadr,sizeof(sadr)) < 0) {
                printf("Couldn't bind requested udp port\n");
                exit(1);
        }

        for (;;)
        {
                if((msglen=recvfrom(sck,msg,sizeof(msg),0,NULL,&dummy)) < 0)
                        printf("Couldn't recvfrom() from udp port\n");
                printf("%.*s\n", msglen, msg);
        }
}