From 54d69bcedcff24bcfe9c32ced6a5623f2ea33c27 Mon Sep 17 00:00:00 2001
From: Akemi Izuko <akemi@noway.moe>
Date: Fri, 31 Jan 2025 13:16:39 -0700
Subject: [PATCH] Lab10: add single thread udp example

---
 lab10/single_thread_udp.c | 143 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 lab10/single_thread_udp.c

diff --git a/lab10/single_thread_udp.c b/lab10/single_thread_udp.c
new file mode 100644
index 0000000..507d7ca
--- /dev/null
+++ b/lab10/single_thread_udp.c
@@ -0,0 +1,143 @@
+#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);
+}