nonagle.c

#include <asm-generic/socket.h>
#include <stdio.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/time.h>
#include <netinet/tcp.h>

#define NONAGLE 1

#define TIMEMS() \
    ({ \
        struct timeval _timeval; \
        gettimeofday(&_timeval, NULL); \
        _timeval.tv_usec; \
    })

void main() {
    pid_t pid = fork();
    struct timeval as;
    
    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    addr.sin_port = htons(1337);

    if (pid == 0) {
        int sock_fd = socket(AF_INET, SOCK_STREAM, 0);
        int nonagle = NONAGLE;
        setsockopt(sock_fd, IPPROTO_TCP, TCP_NODELAY, &nonagle, sizeof(nonagle));
        sleep(1);
        connect(sock_fd, &addr, sizeof(addr));
        perror("connect");

        for (;;) {
            char c = 'A';
            write(sock_fd, &c, 1);
            perror("write");
            write(sock_fd, &c, 1);
            perror("write");
            printf("written %ld\n", TIMEMS());
            sleep(1);
        }
    } else {
        int sock_fd = socket(AF_INET, SOCK_STREAM, 0);
        int reuse = 1;
        setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));
        bind(sock_fd, &addr, sizeof(addr));
        perror("bind");
        listen(sock_fd, 1);
        perror("listen");
        struct sockaddr_in client_addr;
        socklen_t client_len = sizeof(client_addr);
        int client_fd = accept(sock_fd, &client_addr, &client_len);
        perror("accept");

        char buf[256];
        for (;;) {
            int n = read(client_fd, &buf, sizeof(buf));
            perror("read");
            printf("read  %d %ld\n", n, TIMEMS());
        }
    }    
}