Change the inproc:// connection logic

An inproc:// endpoint must exist before we can connect to it. This change
removes the silly sleep(1) hack to wait for the sender thread to come online
and instead does the zmq_bind() in the main thread and the zmq_connect() in the
sender thread.

1 files changed, 46 insertions, 20 deletions

diff --git a/zmq-camera.c b/zmq-camera.c
index a18026d..3be17c6 100644
--- a/zmq-camera.c
+++ b/zmq-camera.c
@@ -34,12 +34,20 @@
 #define FOURCC(a,b,c,d) (unsigned int)((((unsigned int)d)<<24)+\
     (((unsigned int)c)<<16)+(((unsigned int)b)<<8)+a)
 
+/* inproc endpoint used to provide the "local loopback" view of the camera */
+const char local_camera[] = "inproc://local-camera";
+
+/* Sender thread initialiser */
 struct sender_args_t
 {
     const char *endpoint;
     void *ctx;
 };
 
+/*
+ *  Sender thread
+ */
+
 void *sender_thread (void *arg)
 {
     struct sender_args_t *sender_args;
@@ -55,8 +63,8 @@ void *sender_thread (void *arg)
 
     sender_args = (struct sender_args_t *)arg;
 
-    /* Create a ZMQ_PUB socket for sending video data and bind it to both
-       an inproc endpoint for the local loopback view and the endpoint
+    /* Create a ZMQ_PUB socket for sending video data and connect it to both
+       an inproc endpoint for the local loopback view and bind to the endpoint
        specified by the user. */
     s = zmq_socket (sender_args->ctx, ZMQ_PUB);
     assert (s);
@@ -66,9 +74,9 @@ void *sender_thread (void *arg)
             zmq_strerror (errno));
         exit (1);
     }
-    rc = zmq_bind (s, "inproc://local-camera");
+    rc = zmq_connect (s, local_camera);
     if (rc != 0) {
-        fprintf (stderr, "zmq_bind (\"inproc://local-camera\"): %s\n",
+        fprintf (stderr, "zmq_connect (\"%s\"): %s\n", local_camera,
             zmq_strerror (errno));
         exit (1);
     }
@@ -191,6 +199,10 @@ void *sender_thread (void *arg)
     return NULL;
 }
 
+/*
+ *  Print usage and exit.
+ */
+
 void err_usage(void)
 {
     const char usage[] = \
@@ -211,6 +223,10 @@ void err_usage(void)
     exit (1);
 }
 
+/*
+ *  Main thread
+ */
+
 int main (int argc, char *argv [])
 {
     void *ctx, *s;
@@ -239,29 +255,36 @@ int main (int argc, char *argv [])
     ctx = zmq_init (2, 1, 0);
     assert (ctx);
 
-    /* If sending video, start the sender thread */
+    /* Create a ZMQ_SUB socket to receive video data. If we're sending video, 
+       bind to an inproc: endpoint that the sender thread will connect to, 
+       otherwise connect to the endpoint the user specified. */
+    s = zmq_socket (ctx, ZMQ_SUB);
+    assert (s);
     if (is_sender) {
+        rc = zmq_bind (s, local_camera);
+        if (rc != 0) {
+            fprintf (stderr, "zmq_bind (\"%s\"): %s\n", local_camera,
+                zmq_strerror (errno));
+            exit (1);
+        }
+
+        /* Start the sender thread after binding to the inproc: endpoint
+           since this must exist for it to connect. */
         struct sender_args_t sender_args = {endpoint, ctx};
         pthread_t sender;
         rc = pthread_create (&sender, NULL, sender_thread,
             (void*) &sender_args);
         assert (rc == 0);
-        /* XXX */ sleep (1);
+    } 
+    else {
+        rc = zmq_connect (s, endpoint);
+        if (rc != 0) {
+            fprintf (stderr, "zmq_connect (\"%s\"): %s\n", endpoint,
+                zmq_strerror (errno));
+            exit (1);
+        }
     }
 
-    /* Create a ZMQ_SUB socket to receive video data. If we're also sending, 
-       bind to an inproc: endpoint to get the video feed, otherwise bind to
-       the endpoint the user specified. */
-    s = zmq_socket (ctx, ZMQ_SUB);
-    assert (s);
-    if (is_sender)
-        endpoint = "inproc://local-camera";
-    rc = zmq_connect (s, endpoint);
-    if (rc != 0) {
-        fprintf (stderr, "zmq_connect (\"%s\"): %s\n", endpoint,
-            zmq_strerror (errno));
-        exit (1);
-    }
     /* Subscribe to all messages on socket. */
     rc = zmq_setsockopt (s, ZMQ_SUBSCRIBE, "", 0);
     assert (rc == 0);
@@ -317,7 +340,10 @@ int main (int argc, char *argv [])
                exit (1);
             }
             /* Set window title to endpoint we are receiving from */
-            SDL_WM_SetCaption (endpoint, endpoint);
+            if (is_sender)
+                SDL_WM_SetCaption (local_camera, local_camera);
+            else
+                SDL_WM_SetCaption (endpoint, endpoint);
 
             sdl_initialised = 1;
         }