keepalivetest.c

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

int main(int argc, const char *argv[])
{
    if (argc < 4)
    {
        printf("Usage: keepalivetest HOSTNAME PORT KEEPALIVE_TIMEOUT\n");
        return 1;
    }

    const char *hostname = argv[1];
    const int port = atoi(argv[2]);
    const int idle = atoi(argv[3]);

    // 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 = 15;
    // int idle = 1; // working setting...
    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;
    int interval = 75;
    if (setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPINTVL, &interval, sizeof(int)) < 0) {
        printf("Error: Setting TCP_KEEPINTVL failed.\n");
        return 1;
    }

    // int maxpkt = 10;
    int maxpkt = 8;
    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... ");
    }

    int wait_sec = 80;
    while (wait_sec > 0)
    {
        sleep(1);
        printf(".");
        fflush(stdout);
        wait_sec -= 1;
    }
    printf("\n");

    printf("Writing data \n");
    const char *buff = "GET / \n\n";
    size_t written = 0;
    printf("about to write %lu \n", strlen(buff));
    if ((written = write(sockfd, buff, strlen(buff))) < 0)
    {
        printf("Error write to socket: %d \n", errno);
        return 1;
    }

    printf("written %lu \n", written);

    char in_buff[1024];
    ssize_t chunk_size = 0;
    ssize_t read_bytes = 0;
    while ((chunk_size = read(sockfd, &in_buff, sizeof(in_buff))) > 0)
    {
        read_bytes += chunk_size;
        printf(".");
        fflush(stdout);
    }

    // less `xcrun --show-sdk-path`/usr/include/errno.h
    printf("Errno: %d \n", errno);
    printf("Read total bytes: %zd\n", read_bytes);

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

        break;
    }

    // close the socket
    close(sockfd);

    return 0;
}