#include <stdio.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <string.h>
/* Internet socket structures
* are defined in below header */
#include <netinet/in.h>
/* inet_addr is defined in
* below header */
#include <arpa/inet.h>
#include <signal.h>

/* for Read/write API calls*/
#include <unistd.h>

#define PORT 55000
#define TRUE 1

/* IPv6 socket structures for
* server and client */

struct sockaddr_in6 serveraddr, clientaddr;

/* socket file descriptor */
int socket_fd, clientfd;

/* Interrupt_handler – so that CTRL + C can be used to
* exit the program */
void interrupt_handler (int signum) {
        close(socket_fd);
        close(clientfd);

        printf(“socket connection closed\n”);
        exit(0);
}

int main () {
        /* length of client structure received on accept */
        int length;
        char buffer[50];
        char *string = “Hello from Server”;

        /* signal handler to exit out of while 1 loop */
        signal (SIGINT, interrupt_handler);
        signal (SIGPIPE, interrupt_handler);

        /* Part 1 – create the socket */

        if ((socket_fd = socket(AF_INET6, SOCK_STREAM, 0)) < 0) {
                printf(“unable to create the socket\n”);
                exit(0);
        }

        /* Part 2 – create the server connection – fill the structure*/
        serveraddr.sin6_family = AF_INET6;

        /* use loopback address (127.0.0.1)so that
        * the server/client connection
        * can be created on the same machine */
        inet_pton(AF_INET6, “::1”, (void *)(&serveraddr.sin6_addr));
        serveraddr.sin6_port = htons(PORT);

        /* Part 3 – bind and start accepting connections */

        if(0 != bind(socket_fd, (struct sockaddr *)&serveraddr, sizeof(struct sockaddr_in6))) {
                printf(“unable to bind to the socket\n”);
                goto end;
        }

        /* accept upto 5 pending requests
        * and make the server socket a passive socket
        */
        if (listen(socket_fd, 5) == -1) {
                printf(“Listen Failed\n”);
                goto end;
        }

        /* accept is a blocking call and the call would stop further invocation of            code till a client connection is accepted */
        printf(“waiting for connection\n”);
        clientfd = accept(socket_fd, (struct sockaddr *)&clientaddr, &length);

        if (clientfd < 0) {
                 printf(“Unable to connect to Client FD\n”);
                goto end;
        }

        /* read and write data from/to client socket */
        while (TRUE) {
                 /* Use the client socket FD to read data from the client */
                 memset(buffer, 0, sizeof(buffer));
                 read(clientfd, buffer, sizeof(buffer));
                 printf(“%s\n”, buffer);

                 /* write data to the client */
                memset(buffer, 0, sizeof(buffer));
                snprintf(buffer, (strlen(string) + 1), “%s\n”, string);
                write(clientfd, buffer, sizeof(buffer));
        }
end:
        if (clientfd > 0)
                close(clientfd);
        close(socket_fd);

        return 0;
}

#include <stdio.h>
#include <sys/socket.h>
/* Internet socket structures
* are defined in below header */
#include <netinet/in.h>
/* inet_addr is defined in
* below header */
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>

/* For read/write APIs*/
#include <unistd.h>
#define PORT 55000

/* socket file descriptor */
int socket_fd;
/* IPv6 socket structure */
struct sockaddr_in6 sockaddrin;

/* Interrupt_handler so that CTRL +C can be used
* to exit the program */
void interrupt_handler (int signum) {
        close(socket_fd);
        printf(“socket connection closed\n”);
        exit(0);
}

int main () {
        char buffer[50] = {0};
        char *string = “Hello from client”;

        /* signal handler to exit out of while 1 loop */
        signal (SIGINT, interrupt_handler);
        signal (SIGPIPE, interrupt_handler);

        /* Part 1 – create a socket */
        /* create the socket FD */
        socket_fd = socket(AF_INET6, SOCK_STREAM, 0);

        if (socket_fd < 0) {
                printf(“The Socket API call failed\n”);
                exit(0);
        }

        /* Part 2 – allocate server connection details
        * structure for connection */

        /* fill the sockaddr_in6 structure
        * so that it can be connected to the socket */

        sockaddrin.sin6_family = AF_INET6;
        sockaddrin.sin6_port = htons(PORT);

        /* use loopback address (127.0.0.1)so that
        * the server/client connection
        * can be created on the same machine */
        inet_pton(AF_INET6, “::1”, (void *)(&sockaddrin.sin6_addr));

        /* part 3 – connect to the server defined by IP address and port*/
        /* connect to the server */
        if (0 != connect(socket_fd, (struct sockaddr *)&sockaddrin,
(socklen_t)(sizeof(struct sockaddr_in6)))) {
                printf(“Unable to connect\n”);
                /* unable to connect to server */
                goto end;
        }

        /* Part 4 – send/receive data */
        /* read and write data from/to client socket */
        while (1) {

                memset(buffer, 0, sizeof(buffer));
                /* write data to the server */
                snprintf(buffer, (strlen(string) + 1), “%s\n”, string);
                write(socket_fd, buffer, sizeof(buffer));

                memset(buffer, 0, sizeof(buffer));
                read(socket_fd, buffer, sizeof(buffer));
                printf(“%s\n”, buffer);
        }
end:
        close(socket_fd);
}