TCP Server

#include <sys/socket.h>
#include <stdio.h>

int make_server_socket(void) {
    int fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd < 0) { perror("socket"); }
    return fd;
}

#include <sys/socket.h>

void allow_reuse(int fd) {
    int yes = 1;
    setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof yes);
}

#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>

int bind_port(int fd, unsigned short port) {
    struct sockaddr_in addr = {0};
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_port = htons(port);
    if (bind(fd, (struct sockaddr *)&addr, sizeof addr) < 0) {
        perror("bind"); return -1;
    }
    return 0;
}

#include <sys/socket.h>
#include <stdio.h>

int start_listen(int fd) {
    if (listen(fd, 16) < 0) { /* backlog of 16 */
        perror("listen"); return -1;
    }
    return 0;
}

#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>

int accept_one(int listen_fd) {
    struct sockaddr_in cli;
    socklen_t len = sizeof cli;
    int conn = accept(listen_fd, (struct sockaddr *)&cli, &len);
    if (conn < 0) perror("accept");
    return conn;
}

#include <sys/socket.h>
#include <stdio.h>

void handle(int conn) {
    char buf[256];
    ssize_t n = recv(conn, buf, sizeof buf - 1, 0);
    if (n > 0) { buf[n] = 0; printf("got: %s\n", buf); }
}

#include <sys/socket.h>
#include <string.h>

void reply(int conn) {
    const char *msg = "hello from server\n";
    size_t left = strlen(msg);
    const char *p = msg;
    while (left > 0) {
        ssize_t n = send(conn, p, left, 0);
        if (n <= 0) break;
        p += n; left -= (size_t)n;
    }
}

#include <unistd.h>

void serve_loop(int listen_fd, int (*accept_one)(int), void (*handle)(int)) {
    for (;;) {
        int conn = accept_one(listen_fd);
        if (conn < 0) continue;
        handle(conn);
        close(conn); /* done with this client */
    }
}