From 4faf778b6ec4b9d8ab0c19e22d27c76f4c67ab28 Mon Sep 17 00:00:00 2001
From: Oxore <oxore@protonmail.com>
Date: Thu, 14 Dec 2023 23:08:02 +0300
Subject: Impl mutual exchange of UDP messages

---
 client.c | 41 ++++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 11 deletions(-)

(limited to 'client.c')

diff --git a/client.c b/client.c
index 007bf2d..8f4d5ff 100644
--- a/client.c
+++ b/client.c
@@ -3,17 +3,21 @@
 #include <netinet/in.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/socket.h>
 #include <unistd.h>
 
+static unsigned char udp_buffer[UINT16_MAX];
+
 static inline bool IsDigit(char c) { return c >= '0' && c <= '9'; }
 
-static unsigned ParseAddress(char const *str, FILE *log_stream)
+static uint32_t ParseAddress(char const *str, FILE *log_stream)
 {
-    unsigned addr = 0, byte_counter = 0, byte = 0, digits_counter = 0;
+    uint32_t addr = 0;
+    unsigned byte_counter = 0, byte = 0, digits_counter = 0;
     for (size_t i = 0;; i++) {
         char const c = str[i];
         if (c == '\0') {
@@ -74,7 +78,7 @@ int main(int const argc, char *const argv[])
     }
     int const port = atoi(argv[2]);
     if (port <= 0 || port > UINT16_MAX) {
-        fprintf(stderr, "Invalid port specifed\n");
+        fprintf(stderr, "Invalid port specified\n");
         return 1;
     }
     int const fd = socket(AF_INET, SOCK_DGRAM, 0);
@@ -87,14 +91,29 @@ int main(int const argc, char *const argv[])
         .sin_port = htons(port),
         .sin_addr.s_addr = htonl(addr),
     };
-    for (int i = 0; i < 4; i++) {
-        ssize_t const ret = sendto(
-                fd, "hello", 5, 0, (struct sockaddr const *)&serveraddr, sizeof(serveraddr));
-        if (ret < 0) {
-            perror("sendto failed");
-            break;
-        }
-        printf("message sent\n");
+    ssize_t const ret = sendto(
+            fd, "\x2a", 1, 0, (struct sockaddr const *)&serveraddr, sizeof(serveraddr));
+    if (ret < 0) {
+        perror("sendto failed");
+        return 1;
     }
+    printf("message sent\n");
+    struct sockaddr_in source_address;
+    socklen_t source_address_len = sizeof(source_address);
+    int const length = recvfrom(
+            fd,
+            udp_buffer,
+            sizeof(udp_buffer) - 1,
+            0,
+            (struct sockaddr*)&source_address,
+            &source_address_len);
+    (void) length;
+    uint32_t const addr2 = ntohl(source_address.sin_addr.s_addr);
+    uint8_t const a0 = addr2 >> 24;
+    uint8_t const a1 = addr2 >> 16;
+    uint8_t const a2 = addr2 >> 8;
+    uint8_t const a3 = addr2;
+    uint16_t const port2 = ntohs(source_address.sin_port);
+    printf("Received: %u from %u.%u.%u.%u:%u\n", udp_buffer[0], a0, a1, a2, a3, port2);
     close(fd);
 }
-- 
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