IPv6 server & client in C

client.c

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

void ping(int s, char *message)
{
    char buf[8192];

    strncpy(buf, message, sizeof(buf));
    send(s, buf, strlen(buf), 0);
    recv(s, buf, 8192, 0);
    strtok(buf, "\n");
    puts(buf);
}

int main()
{
    int s;
    struct sockaddr_in6 addr;

    s = socket(AF_INET6, SOCK_STREAM, 0);
    addr.sin6_family = AF_INET6;
    addr.sin6_port = htons(5000);
    inet_pton(AF_INET6, "::1", &addr.sin6_addr);
    connect(s, (struct sockaddr *)&addr, sizeof(addr));

    ping(s, "hoge\n");
    ping(s, "fuga\n");
    ping(s, "piyo\n");

    close(s);
    return 0;
}

result.txt

$ gcc server.c -o server

$ gcc client.c -o client

$ ./server &
[1] 6422

$ netstat -ant
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:6010          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:6011          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN
tcp        0    216 192.168.56.2:22         192.168.56.1:54688      ESTABLISHED
tcp        0      0 192.168.56.2:22         192.168.56.1:59121      ESTABLISHED
tcp6       0      0 :::22                   :::*                    LISTEN
tcp6       0      0 ::1:6010                :::*                    LISTEN
tcp6       0      0 ::1:6011                :::*                    LISTEN
tcp6       0      0 :::5000                 :::*                    LISTEN

$ ./client
hoge
fuga
piyo

server.c

#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

void handle_client(int c)
{
    char buf[8192];
    char *lastpos;
    int size;

    while (1) {
        size = recv(c, buf, 8192, 0);
        if (size == 0) {
            break;
        }
        lastpos = strchr(buf, '\n');
        send(c, buf, lastpos+1-buf, 0);
    }
}

int main()
{
    int s, c;
    int reuseaddr = 1;
    struct sockaddr_in6 addr;
    int pid;

    s = socket(AF_INET6, SOCK_STREAM, 0);
    setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &reuseaddr, sizeof(reuseaddr));

    addr.sin6_family = AF_INET6;
    addr.sin6_port = htons(5000);
    addr.sin6_addr = in6addr_any;

    bind(s, (struct sockaddr *)&addr, sizeof(addr));
    listen(s, 5);

    while (1) {
        c = accept(s, NULL, NULL);
        pid = fork();
        if (pid == -1) {
            exit(1);
        } else if (pid == 0) {
            close(s);
            handle_client(c);
            close(c);
            return 0;
        } else {
            close(c);
            waitpid(pid, NULL, 0);
        }
    }
}