TCP socket consumption in C

build.sh

#!/bin/sh

set -xe

cc -Wall -Werror -std=c11 -pedantic -o main main.c

main.c

#include <sys/socket.h>
#include <sys/types.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <stdarg.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <netdb.h>

#define SERVER_PORT 80

#define MAXLINE 4096

#define USE_TCP 0

#define SA struct sockaddr

void err_n_die(const char *fmt, ...) {
  int errno_save = errno;
  va_list ap;

  va_start(ap, fmt);

  vfprintf(stderr, fmt, ap);
  fprintf(stderr, "\n");
  fflush(stderr);

  if (errno_save != 0) {
    fprintf(stderr, "(errno = %d): %s\n", errno_save, strerror(errno_save));
    fprintf(stderr, "\n");
    fflush(stderr);
  }

  va_end(ap);

  exit(1);
}

int main(int argc, char *argv[]) {
  int sockfd;
  int n;
  int sendbytes;
  struct sockaddr_in serveraddr;
  char sendline[MAXLINE];
  char recvline[MAXLINE];

  if(argc != 2) {
    err_n_die("usage: %s <server address>", argv[0]);
  }

  if ((sockfd = socket(AF_INET, SOCK_STREAM, USE_TCP)) < 0) {
    err_n_die("Error while creating the socket!");
  }

  bzero(&serveraddr, sizeof(serveraddr));
  serveraddr.sin_family = AF_INET;
  serveraddr.sin_port = htons(SERVER_PORT);

  if (inet_pton(AF_INET, argv[1], &serveraddr.sin_addr) <= 0) {
    err_n_die("inet_pton error for %s", argv[1]);
  }

  if (connect(sockfd, (SA *) &serveraddr, sizeof(serveraddr)) < 0) {
    err_n_die("connect failed!");
  }

  sprintf(sendline, "GET / HTTP/1.1\r\n\r\n");
  sendbytes = strlen(sendline);

  if (write(sockfd, sendline, sendbytes) != sendbytes) {
    err_n_die("write error");
  }

  memset(recvline, 0, MAXLINE);

  while ((n = read(sockfd, recvline, MAXLINE - 1)) > 0) {
    printf("%s", recvline);
    memset(recvline, 0, MAXLINE);
  }

  if (n < 0) {
    err_n_die("read errror");
  }

  return 0;
}