using getpeername sample c function code

/* getpeer.c

 * Demonstrate getpeername(2):

 */

 #include <stdio.h>

 #include <unistd.h>

 #include <stdlib.h>

 #include <errno.h>

 #include <string.h>

 #include <sys/types.h>

 #include <sys/stat.h>

 #include <sys/socket.h>

 #include <sys/un.h>

 #include <netinet/in.h>

 #include <arpa/inet.h>

/*

 * This function accepts as input a socket

 * for which a peer socket address must be

 * determined for it. Then the address

 * is converted into a string and returned.

 *

 * If an error occurs, NULL is returned.

 */

 char * peer_addr(int s, char *buf, size_t bufsiz) {

    int z; /* Status return code */

    struct sockaddr_in adr_inet;/* AF_INET */

    int len_inet; /* length */

/*

 * Obtain the address of the socket:

 */

    len_inet = sizeof adr_inet;

    z = getpeername(s, (struct sockaddr *)&adr_inet, &len_inet);

    if ( z == -1) {

       return NULL; /* Failed */

    }

/*

 * Convert address into a string

 * form that can be displayed:

 */

    z = snprintf(buf,bufsiz, "%s:%u",

    inet_ntoa(adr_inet.sin_addr),

   (unsigned)ntohs(adr_inet.sin_port));

    if ( z == -1 ) {

       return NULL; /* Buffer too small */

    }

    return buf;

 }