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:v/\S/d

IPV6 Hostname Resolution in Linx

/* IPV6 resolving host name
arg: hostname*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#include <errno.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main (int argc, char *argv[])
{
                struct addrinfo *res;
                char ip_addr[INET6_ADDRSTRLEN];
                struct sockaddr_in6 *saddr;
                socklen_t       len ;

                saddr = NULL;

                if( argc != 2 )
                {
                                return -1;
                }

                res = NULL;

                printf("host[%s]\n", argv[1]);

                getaddrinfo(argv[1], NULL ,NULL,&res);

                if ( res != NULL )
                {
                                printf("ai_flags -> %i\n", res->ai_flags) ;
                                printf("ai_family -> %i\n", res->ai_family) ;
                                printf("ai_socktype -> %i\n", res->ai_socktype) ;
                                printf("ai_protocol -> %i\n", res->ai_protocol) ;
                                printf("ai_addrlen -> %i\n", res->ai_addrlen) ;

                                if ( res->ai_family == 2 )
                                {
                                        struct sockaddr_in *saddr = (struct sockaddr_in*)res->ai_addr;
                                        printf("ai_addr hostname ->  %s\n", inet_ntoa( saddr->sin_addr));
                                   }

                                if ( res->ai_family == 10 )
                                {
                                        saddr = (struct sockaddr_in6*)res->ai_addr;

                                        inet_ntop(AF_INET6, &saddr->sin6_addr, ip_addr, INET6_ADDRSTRLEN);
                                    printf("address[%s]\n", ip_addr);
                                 }
                }
                else
                {
                                printf("host is not found\n");
                }

                freeaddrinfo(res);

                return 0 ;
}

IPV6 Host Name Resolving in Linux

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>

int main(int argc, char *argv[])
{

                char tmphstbuf [4096];
                size_t hstbuflen  = sizeof (tmphstbuf);
                struct hostent hostinfo_buf = {0,};
                struct hostent *hostresult = NULL;
                int herr ;

                int ret = -1 ;

                size_t len;

                char ip_addr[INET6_ADDRSTRLEN] = {0,};
                 struct sockaddr_in6 addr;

                len = sizeof(tmphstbuf);

                ret = gethostbyname_r(argv[1], &hostinfo_buf, tmphstbuf, len, &hostresult, &herr);


                printf("Addresses:\t");
                inet_ntop(AF_INET6, hostinfo_buf.h_addr_list[0], ip_addr, INET6_ADDRSTRLEN);
                 printf("%s\n", ip_addr);


}

/* Keep add your hostnames in /etc/hosts file */

Simple UDP EchoServer

/*
 * @filename : server.c
 * @brief:  Server Program
 * */
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>


#define MAX_LINE 256

int         conn_count=0;
void *HandlingClient(void *);

int main(int argc,char *argv[])
{
        struct sockaddr_in  serv_addr,  client_addr;
        int           sockid, newsockid, len, ret;
         char  buf[MAX_LINE];

        if(argc < 2 )
        {
                printf("usage: %s <port>\n", argv[0]);
                return -1;
        }

        sockid = socket(AF_INET,SOCK_DGRAM, 0);
        if(sockid < 0 )
        {
                printf("Failed to get socket\n");
                return -1;
        }

        serv_addr.sin_family = AF_INET;
        serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
        serv_addr.sin_port = htons(atoi(argv[1]));

        if((bind(sockid,(struct sockaddr*)&serv_addr,sizeof(serv_addr))) != 0)
        {
                printf("Failed to bind\n");
                return -2;
        }

        len = sizeof(client_addr);

        while(1)
        {
                ret = recvfrom(sockid,&buf,MAX_LINE,0, (struct sockaddr*)&client_addr, &len);
                if ( ret == 0 )
                {
                        break;
                }
                else if ( ret < 0 )
                {
                        printf("Error Occurs Err[#%d,%s]\n", errno, strerror(errno) );
                        break;
                }

                if(!strncasecmp(buf,"bye",3))
                {
                        break;
                }

                /* send back to client*/
                if( (ret = sendto(sockid, &buf, ret, 0, (struct sockaddr*)&client_addr, sizeof(client_addr))) <= 0 )
                {
                        printf("Client coultn't send message to server\n");
                        break;
                }
        }

        close(sockid);

        return 0;
}

/*
 *   @filename : client.c
 *     @brief: Client Program
 *     */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define MAX_LINE  256


void *SendReceive(void* sockid);

int main(int argc,char *argv[])
{
        struct sockaddr_in  serv_addr, cli_addr ;
        int     sockid;
        char  buf[MAX_LINE],sendbuf[MAX_LINE];
        int   length,ret ;
        socklen_t len;

        if(argc < 3 )
        {
                printf("usage: %s <server-address> <port> \n",argv[0]);
                return -1;
        }

        sockid = socket(AF_INET,SOCK_DGRAM,0) ;
        if(sockid == -1 )
        {
                printf("Failed to get socket\n");
                return -2;
        }

        serv_addr.sin_family = AF_INET ;
        serv_addr.sin_addr.s_addr = inet_addr(argv[1]) ;
        serv_addr.sin_port = htons(atoi(argv[2])) ;

        len = 1;

        while(1)
        {
                memset(buf,0,sizeof(buf));
                if(fgets(buf,MAX_LINE,stdin) == NULL )
                {
                        printf ("received EOF from stdin\n");
                        break;
                }

                length = strlen(buf);

                if( (ret = sendto(sockid, &buf, length, 0, (struct sockaddr*)&serv_addr, sizeof(serv_addr))) <= 0 )
                {
                        printf("Client coultn't send message to server\n");
                        break;
                }

                ret = recvfrom(sockid,&buf,MAX_LINE,0, (struct sockaddr*)&cli_addr, &len);
                if ( ret == 0 )
                {
                        printf("Error Occurs Err[#%d,%s]\n", errno, strerror(errno) );
                        break;
                }
                else if ( ret < 0 )
                {
                        printf("Error Occurs Err[#%d,%s]\n", errno, strerror(errno) );
                        break;
                }
                printf("%s",buf);
        }

        close(sockid);

        return 0;
}

MESSAGE="Echo Program Built Successfully"
MESSAGE1 = " ------------------------- "

CC      = gcc

CFLAGS  = -g -I./include

all:  server client
        @echo $(MESSAGE1)
        @echo $(MESSAGE)
        @echo $(MESSAGE1)

server: server.o
        ${CC} -o $@ server.o

client: client.o
        ${CC} -o $@ client.o

clean:
        -@rm *.o

distclean:  clean
        -@rm server client