/* * code for example client program that uses UDP * */
#ifndef unix
#include <winsock2.h>
/* also include Ws2_32.lib library in linking options */
#else
#define closesocket close
#define SOCKET int
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
/* also include xnet library for linking; on command line add: -lxnet */
#endif

#include <stdio.h>
#include <string.h>

#define PORT 1200
                                    /* default protocol port number */

char    localhost[] = "localhost";  /* default host name            */
/*------------------------------------------------------------------------
 * Program:   client
 *
 * Purpose:   allocate a socket, connect to a server, and print all output
 *
 *------------------------------------------------------------------------
 */
int main()
{
    struct  hostent  *ptrh;  /* pointer to a host table entry       */
    struct  protoent *ptrp;  /* pointer to a protocol table entry   */
    struct  sockaddr_in sad; /* structure to hold an IP address     */
    int     alen;            /* length of address                   */
    SOCKET  sd;              /* socket descriptor - integer         */
    char    host[256];       /* pointer to host name                */

#ifdef WIN32
    WSADATA wsaData;
    if(WSAStartup(0x0101, &wsaData)!=0)
    {
        fprintf(stderr, "Windows Socket Init failed: %d\n", GetLastError());
        exit(1);
    }
#endif

    memset((char *)&sad,0,sizeof(sad)); /* clear sockaddr structure */
    sad.sin_family = AF_INET;         /* set family to Internet     */

    strcpy(host,localhost); // host=localhost

    /* Convert host name to equivalent IP address and copy to sad. */
    ptrh = gethostbyname(host);
    if ( ((char *)ptrh) == NULL ) {
        fprintf(stderr, "invalid host: %s\n", host);
        exit(1);
    }
    memcpy(&sad.sin_addr, ptrh->h_addr, ptrh->h_length);

    sad.sin_port = htons((u_short)PORT); /* use default port number */
    alen = sizeof(sad);

    /* Map TCP transport protocol name to protocol number. */
    ptrp = getprotobyname("udp");
    if ( ptrp == 0) {
        fprintf(stderr, "cannot map \"udp\" to protocol number\n");
        exit(1);
    }

    /* Create a socket. */
    sd = socket(PF_INET, SOCK_DGRAM, ptrp->p_proto);
    if (sd < 0) {
        fprintf(stderr, "soclet creation failed\n");
        exit(1);
    }

    {
        int  n;              /* number of characters received       */
        int  m;              /* number of characters sent back      */
        char buf[1000];      /* buffer for data from the server     */

        /* Send data to socket in order to request reply. */
        m = 1;              /* sned zero bytes */
        m = sendto(sd,buf,m,0,(struct sockaddr*)&sad,alen);
        if(m<0)
        {
            fprintf(stderr,"Error in sending");
        }
        else
        {
            /* Read data from socket and write to user's screen. */
            n = recvfrom(sd,buf,sizeof(buf),0,(struct sockaddr*)&sad,&alen);
            if (n > 0) {
                buf[n]='\0';    /* just in case place the termination at the end of the string */
                printf("%s", buf);
            }
        }
    }

    /* Close the socket. */
    closesocket(sd);

#ifdef WIN32
    WSACleanup();                      /* release use of winsock.dll */
#endif

    /* Terminate the client program gracefully. */
    return(0);
}