A very messy demo of a broadcast

2026-01-04 16:24:36 +01:00
commit 36ae15c320
5 changed files with 369 additions and 0 deletions
@@ -0,0 +1,143 @@
+#include "commands.h"
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/msg.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#define send(queue_id, msgbuf_ptr)                                             \
+  msgsnd(queue_id, msgbuf_ptr, sizeof(*(msgbuf_ptr)) - sizeof(long), 0)
+
+static void cleanup_queue(int qid) {
+  if (qid != -1) {
+    msgctl(qid, IPC_RMID, NULL);
+  }
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    fprintf(stderr, "Usage: %s <client_id>\n", argv[0]);
+    return 1;
+  }
+
+  char *client_id = argv[1];
+
+  int client_queue_id = msgget(IPC_PRIVATE, IPC_CREAT | 0666);
+  if (client_queue_id == -1) {
+    perror("msgget(client) failed");
+    return 1;
+  }
+
+  int server_queue_id = -1;
+  const char *id_path = "/home/piotr/server_queue_id";
+  FILE *f = fopen(id_path, "rb");
+
+  if (fread(&server_queue_id, sizeof(int), 1, f) != 1) {
+    fprintf(stderr, "Failed to read server queue id from %s\n", id_path);
+    server_queue_id = -1;
+  }
+  fclose(f);
+
+  msgbuf_t msg;
+  memset(&msg, 0, sizeof(msgbuf_t));
+  msg.mtype = Login;
+  /* command field holds client id for login */
+  strncpy(msg.command, client_id, COMMAND_LENGTH - 1);
+  /* message field holds the client's queue id as string */
+  snprintf(msg.message, MESSAGE_LENGTH, "%d", client_queue_id);
+
+  if (msgsnd(server_queue_id, &msg, sizeof(msg) - sizeof(long), 0) == -1) {
+    perror("msgsnd(login) failed");
+    cleanup_queue(client_queue_id);
+    return 1;
+  }
+
+  /* Wait for login response (server replies with mtype = Login) */
+  msgbuf_t resp;
+  ssize_t r =
+      msgrcv(client_queue_id, &resp, sizeof(resp) - sizeof(long), Login, 0);
+  if (r == -1) {
+    perror("msgrcv(login response) failed");
+    cleanup_queue(client_queue_id);
+    return 1;
+  }
+
+  if (resp.stype != ACK_ACCEPTED) {
+    fprintf(stderr, "Login rejected: code=%d\n", resp.stype);
+    cleanup_queue(client_queue_id);
+    return 1;
+  }
+
+  printf("Login accepted for id '%s'\n", client_id);
+
+  /* Send a test message to the server */
+  msgbuf_t test = {
+      .mtype = Message,
+      .sender = "the_only_one",
+  };
+  snprintf(test.message, MESSAGE_LENGTH, "Hello from %s", client_id);
+
+  if (msgsnd(server_queue_id, &test, sizeof(test) - sizeof(long), 0) == -1) {
+    printf("DEBUG: test.mtype = %u\n", test.mtype);
+    perror("failed while sending a test message");
+    cleanup_queue(client_queue_id);
+    return 1;
+  }
+
+  printf("Sent test message to server: \"%s\"\n", test.message);
+
+  /* Now wait for server forwarded message(s) and a signal ack.
+     We'll wait until we've seen both a Message and a Signal ack or timeout. */
+  int seen_message = 0;
+  int seen_ack = 0;
+  const int MAX_ITER = 10;
+
+  // for (int i = 0; i < MAX_ITER && !(seen_message && seen_ack); ++i) {
+  while (1) {
+    msgbuf_t incoming;
+    ssize_t got = msgrcv(client_queue_id, &incoming,
+                         sizeof(incoming) - sizeof(long), 0, 0);
+    perror("Got a message damn");
+    if (got == -1) {
+        perror("msgrcv(incoming) failed");
+
+      if (errno == EINTR) {
+        continue;
+      }
+      perror("msgrcv(incoming) failed");
+      break;
+    }
+
+    switch (incoming.mtype) {
+    case Message:
+      printf("Received Message: \"%s\"\n", incoming.message);
+      seen_message = 1;
+      break;
+    case Signal:
+      printf("Received Signal: code=%d\n", incoming.stype);
+      if (incoming.stype == ACK_ACCEPTED || incoming.stype == ACK_DELIVERED) {
+        seen_ack = 1;
+      }
+      break;
+    default:
+      printf("Received unknown mtype=%ld stype=%d\n", (long)incoming.mtype,
+             incoming.stype);
+      break;
+    }
+  }
+
+  if (!seen_message) {
+    fprintf(stderr, "Did not receive forwarded message from server\n");
+  }
+  if (!seen_ack) {
+    fprintf(stderr, "Did not receive ack from server\n");
+  }
+
+  /* Logout/cleanup: remove our queue */
+  cleanup_queue(client_queue_id);
+  printf("Client exiting\n");
+  return 0;
+}