A small utility to test TCP keep-alive on macOS

keepalivetest.c

//
//  keepalivetest.c
//
//  Created by Felix Deimel on 07.11.19
//  Copyright (c) 2019 Felix Deimel
//
//  [INSTRUCTIONS]
//
//  Compile with "cc -o keepalivetest keepalivetest.c"
//  Run with "./keepalivetest HOSTNAME PORT"
//

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <netinet/tcp.h>

int main(int argc, const char * argv[]) {
    if (argc < 3) {
        printf("Usage: keepalivetest HOSTNAME PORT\n");
        return 1;
    }
    
    const char* hostname = argv[1];
    const int port = atoi(argv[2]);
    
    // socket create and varification
    int sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    
    if (sockfd == -1) {
        printf("Error: Socket creation failed.\n");
        return 1;
    }
    
    // enable TCP keep-alive
    int enablekeepalive = 1;
    if (setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &enablekeepalive, sizeof(int)) < 0) {
        printf("Error: Setting SO_KEEPALIVE failed.\n");
        return 1;
    }

    int idle = 1;
    if (setsockopt(sockfd, IPPROTO_TCP, /* TCP_KEEPIDLE */ TCP_KEEPALIVE, &idle, sizeof(int)) < 0) {
        printf("Error: Setting TCP_KEEPALIVE failed.\n");
        return 1;
    }

    int interval = 1;
    if (setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPINTVL, &interval, sizeof(int)) < 0) {
        printf("Error: Setting TCP_KEEPINTVL failed.\n");
        return 1;
    }

    int maxpkt = 10;
    if (setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPCNT, &maxpkt, sizeof(int)) < 0) {
        printf("Error: Setting TCP_KEEPCNT failed.\n");
        return 1;
    }
    
    // assign IP and Port
    struct sockaddr_in servaddr;
    bzero(&servaddr, sizeof(servaddr));
    
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = inet_addr(hostname);
    servaddr.sin_port = htons(port);

    // connect the client socket to server socket
    if (connect(sockfd, (const struct sockaddr *)&servaddr, sizeof(servaddr)) != 0) {
        printf("Error: Connection with the server failed.\n");
        return 1;
    } else {
        printf("Connected to the server.\nPress enter to close the connection... ");
    }

    for (;;) {
        while (getchar() != '\n')
            ;
        
        break;
    }

    // close the socket
    close(sockfd);
    
    return 0;
}