#include <stdio.h> #include <stdlib.h>#include <errno.h> #include <string.h> #include <netdb.h> #include <sys/types.h> #include <netinet/in.h> #include <sys/socket.h> #define PORT 5000                      // The port which is communicate with server#define LENGTH 512                     // Buffer lengthint main(int argc, char *argv[]){   int sockfd;                        // Socket file descriptor    int num;                           // Counter of received bytes      char sdbuf[LENGTH];                // Receive buffer    struct sockaddr_in addr_remote;    // Host address information    char sdstr[]= {"SmartARM22000 UDP Experiment."};            /* Check parameters number */    if (argc != 2)                         {            printf ("ERROR: Please enter Host IP address follow by 'gdclient'\n");        return (0);    }    /* Get the Socket file descriptor */    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)    {        printf("ERROR: Cannot obtain Socket Descriptor!\n");        return (0);    }        /* Fill the socket address struct */    addr_remote.sin_family = AF_INET;                   // Protocol Family    addr_remote.sin_port = htons(PORT);                 // Port number    inet_pton(AF_INET, argv[1], &addr_remote.sin_addr); // Net Address    bzero(&(addr_remote.sin_zero), 8);                  // Flush the rest of struct      /* Try to connect the server */    bzero(sdbuf,LENGTH);    num = sendto(sockfd, sdstr, strlen(sdstr), 0, (struct sockaddr *)&addr_remote, sizeof(struct sockaddr_in));    if( num < 0 )    {        printf ("ERROR: Cannot send your data!\n", argv[1], num);    }    else    {            printf ("OK: Sent to %s total %d bytes !\n", argv[1], num);    }    close (sockfd);    return (0);}