Quick and dirty rewritten code from daytimetcpcli.c

main.c

#include <stdio.h>
#include <strings.h>
#include <unistd.h>
#include <memory.h>
#include "/usr/include/netinet/in.h"
#include "/usr/include/arpa/inet.h"

#define MAXLINE 4096

int main(int argc, char **argv) {
    int					sockfd, n;
    char				recvline[MAXLINE + 1];
    struct sockaddr_in	servaddr;

    if (argc != 2) {
        printf("usage: a.out <IPaddress>");
        return -1;
    }

    if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("socket error");
        return -1;
    }

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port   = htons(13);	/* daytime server */
    if (inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0) {
        printf("inet_pton error for %s", argv[1]);
        return -1;
    }

    // clear contents on sin_zero manually
    // https://silviocesare.wordpress.com/2007/10/22/setting-sin_zero-to-0-in-struct-sockaddr_in/
    memset(&servaddr.sin_zero, 0, sizeof(servaddr.sin_zero));

    if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) {
        printf("connect error");
        return -1;
    }
    
    while ( (n = read(sockfd, recvline, MAXLINE)) > 0) {
        recvline[n] = 0;	/* null terminate */
        if (fputs(recvline, stdout) == EOF) {
            printf("fputs error");
            return -1;
        }
    }
    if (n < 0) {
        printf("read error");
        return -1;
    }

    return 0;
}