379_demos/lab10/single_thread_udp.c

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

int udp_create_server_socket() {
    char* hostname = "localhost";
    char* port = "9004";

    struct addrinfo hints = {0};
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_protocol = IPPROTO_UDP;
    hints.ai_flags = AI_PASSIVE;

    struct addrinfo* res;
    int ret = getaddrinfo(hostname, port, &hints, &res);

    if (ret != 0) {
        perror("getaddrinfo");
        return -1;
    }

    int sfd = -1;
    for (struct addrinfo* rp = res; rp != NULL; rp = rp->ai_next) {
        sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
        if (sfd == -1) {
            perror("socket");
            continue;
        }

        int bind_errno = bind(sfd, rp->ai_addr, rp->ai_addrlen);
        if (bind_errno == -1) {
            perror("bind");
            close(sfd);
            sfd = -1;
            continue;
        }

        break;
    }

    freeaddrinfo(res);

    if (sfd == -1) {
        fprintf(stderr, "Failed to create socket\n");
        close(sfd);
        return -1;
    }

    return sfd;
}

int udp_client_socket(struct sockaddr** socket_addr, socklen_t* addr_len) {
    char* hostname = "localhost";
    char* port = "9004";

    struct addrinfo hints = {0};
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_protocol = IPPROTO_UDP;

    struct addrinfo* res;
    int ret_err = getaddrinfo(hostname, port, &hints, &res);

    if (ret_err != 0) {
        perror("getaddrinfo");
        return -1;
    }

    int sfd;
    for (struct addrinfo* rp = res; rp != NULL; rp = rp->ai_next) {
        sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
        if (sfd == -1) {
            perror("socket");
            continue;
        }

        *socket_addr = rp->ai_addr;
        *socket_addr = malloc(rp->ai_addrlen);
        memcpy(*socket_addr, rp->ai_addr, rp->ai_addrlen);
        *addr_len = rp->ai_addrlen;
        break;
    }

    freeaddrinfo(res);
    if (sfd == -1) {
        fprintf(stderr, "Failed to create socket\n");
        close(sfd);
        return -1;
    }

    return sfd;
}

int main(void) {
    struct sockaddr* socket_addr;
    socklen_t addr_len;

    int sfd_server = udp_create_server_socket();
    int sfd_client = udp_client_socket(&socket_addr, &addr_len);

    printf("Got a server socket: %d\n", sfd_server);
    printf("Got a client socket: %d\n", sfd_client);

    if (sfd_server == -1 || sfd_client == -1) {
        if (sfd_server != -1) close(sfd_server);
        if (sfd_client != -1) close(sfd_client);
        return 1;
    }

    sleep(10);

    char* my_string = "one two three";

    int ret = sendto(
        sfd_client,
        my_string,
        strlen(my_string) + 1,
        0,
        socket_addr,
        addr_len
    );
    if (ret == -1) {
        perror("send");
        return 0;
    }

    char buf[10000];
    ret = recv(sfd_server, (void*) buf, 10000 * sizeof(char), 0);
    if (ret == -1) {
        perror("recv");
        return 0;
    }

    printf("OMG, I just totes got a message: `%s`\n", buf);

    close(sfd_server);
    close(sfd_client);
}