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

int open_clientfd(char *hostname, char *port);

#define MAXLINE 512

/* usage: ./echoclient host port */
int main(int argc, char *argv[])
{
    int clientfd;
    size_t n;
    char *host, *port, buf[MAXLINE];
 
    host = argv[1];
    port = argv[2];

    clientfd = open_clientfd(host, port);
    if (clientfd < 0) {
	if (clientfd == -1)
	    fprintf(stderr, "%s:%s: %s\n", host, port, strerror(errno));
	exit(1);
    }

    while (fgets(buf, sizeof buf - 1, stdin) != NULL) {
        write(clientfd, buf, strlen(buf));
        n = read(clientfd, buf, sizeof buf - 1);
        if (n != -1) {
	    buf[n] = '\0';
	    fputs(buf, stdout);
	}
    }
    close(clientfd);
    exit(0);
}

int open_clientfd(char *hostname, char *port)
{
    int clientfd;
    struct addrinfo hints;
    struct addrinfo *hostaddresses = NULL;
    struct addrinfo *addr;
    int error;

    /* Find out the server's IP address and port */
    memset(&hints, 0, sizeof hints);
    hints.ai_flags = AI_ADDRCONFIG | AI_V4MAPPED;
    hints.ai_family = AF_INET6;
    hints.ai_socktype = SOCK_STREAM;

    error = getaddrinfo(hostname, port, &hints, &hostaddresses);
    if (error != 0) {
        freeaddrinfo(hostaddresses);
        fprintf(stderr, "%s:%s: %s\n", hostname, port, gai_strerror(error));
        return -1;
    }

    /* Walk the address list to find one that we can connect to */
    for (addr = hostaddresses; addr != NULL; addr = addr->ai_next) {
        /* We take advantage of the fact that AF_* and PF_* are identical */
        clientfd = socket(addr->ai_family,
          addr->ai_socktype, addr->ai_protocol);
        if (clientfd == -1)
            continue;                   /* Socket failed, try next */

        /* Establish a connection with the server */
        if (connect(clientfd, addr->ai_addr, addr->ai_addrlen) != -1)
            break;                      /* Success! */
        close(clientfd);                /* Connect failed; try another */
    }
      
    freeaddrinfo(hostaddresses);
    if (addr == NULL)
        return -1;                      /* All failed; check errno for cause */
    return clientfd;
}