Fix #3: use one socket connect per request

Previously all requests shared the same connection which meant that the client
had to wait that a request finished until it could issue another request.
Otherwise, replies could end up for the wrong request causing all kinds of
problems. This synchronous request-reply model could not be kept because of
inherent asynchronicity of certain mechanisms (e.g. grab + software trigger).

This change removes the always-open socket connection and replaces it with a new
connection per request. Due to the OS multiplexing, replies cannot be mistaken.

3 files changed, 66 insertions, 88 deletions

diff --git a/uca-net-camera.c b/uca-net-camera.c
index daf177f..9750758 100644
--- a/uca-net-camera.c
+++ b/uca-net-camera.c
@@ -49,11 +49,11 @@ static GParamSpec *net_properties[N_PROPERTIES] = { NULL, };
 struct _UcaNetCameraPrivate {
     GError              *construct_error;
     gchar               *host;
-    GSocketConnection   *connection;
     GSocketClient       *client;
     gsize                size;
 };
 
+
 static gboolean
 send_default_message (GSocketConnection *connection, UcaNetMessageType type, GError **error)
 {
@@ -94,13 +94,23 @@ handle_default_reply (GSocketConnection *connection, UcaNetMessageType type, GEr
     return FALSE;
 }
 
+static GSocketConnection *
+connect_socket (UcaNetCameraPrivate *priv, GError **error)
+{
+    return g_socket_client_connect_to_host (priv->client, priv->host, UCA_NET_DEFAULT_PORT, NULL, error);
+}
+
 static void
-request_call (GSocketConnection *connection, UcaNetMessageType type, GError **error)
+request_call (UcaNetCameraPrivate *priv, UcaNetMessageType type, GError **error)
 {
-    if (!send_default_message (connection, type, error))
-        return;
+    GSocketConnection *connection;
+
+    connection = connect_socket (priv, error);
 
-    handle_default_reply (connection, type, error);
+    if (send_default_message (connection, type, error))
+        handle_default_reply (connection, type, error);
+
+    g_object_unref (connection);
 }
 
 static void
@@ -122,8 +132,7 @@ uca_net_camera_start_recording (UcaCamera *camera,
 
     priv = UCA_NET_CAMERA_GET_PRIVATE (camera);
     priv->size = width * height * (bits > 8 ? 2 : 1);
-
-    request_call (priv->connection, UCA_NET_MESSAGE_START_RECORDING, error);
+    request_call (priv, UCA_NET_MESSAGE_START_RECORDING, error);
 }
 
 static void
@@ -131,7 +140,7 @@ uca_net_camera_stop_recording (UcaCamera *camera,
                                GError **error)
 {
     g_return_if_fail (UCA_IS_NET_CAMERA (camera));
-    request_call (UCA_NET_CAMERA_GET_PRIVATE (camera)->connection, UCA_NET_MESSAGE_STOP_RECORDING, error);
+    request_call (UCA_NET_CAMERA_GET_PRIVATE (camera), UCA_NET_MESSAGE_STOP_RECORDING, error);
 }
 
 static void
@@ -139,7 +148,7 @@ uca_net_camera_start_readout (UcaCamera *camera,
                               GError **error)
 {
     g_return_if_fail (UCA_IS_NET_CAMERA (camera));
-    request_call (UCA_NET_CAMERA_GET_PRIVATE (camera)->connection, UCA_NET_MESSAGE_START_READOUT, error);
+    request_call (UCA_NET_CAMERA_GET_PRIVATE (camera), UCA_NET_MESSAGE_START_READOUT, error);
 }
 
 static void
@@ -147,7 +156,7 @@ uca_net_camera_stop_readout (UcaCamera *camera,
                              GError **error)
 {
     g_return_if_fail (UCA_IS_NET_CAMERA (camera));
-    request_call (UCA_NET_CAMERA_GET_PRIVATE (camera)->connection, UCA_NET_MESSAGE_STOP_READOUT, error);
+    request_call (UCA_NET_CAMERA_GET_PRIVATE (camera), UCA_NET_MESSAGE_STOP_READOUT, error);
 }
 
 static void
@@ -158,6 +167,7 @@ uca_net_camera_write (UcaCamera *camera,
                       GError **error)
 {
     UcaNetCameraPrivate *priv;
+    GSocketConnection *connection;
     GOutputStream *output;
     gssize bytes_left;
     gchar *buffer;
@@ -166,7 +176,8 @@ uca_net_camera_write (UcaCamera *camera,
     g_return_if_fail (UCA_IS_NET_CAMERA (camera));
 
     priv = UCA_NET_CAMERA_GET_PRIVATE (camera);
-    output = g_io_stream_get_output_stream (G_IO_STREAM (priv->connection));
+    connection = connect_socket (priv, error);
+    output = g_io_stream_get_output_stream (G_IO_STREAM (connection));
     request.size = size;
     strncpy (request.name, name, sizeof (request.name));
 
@@ -187,7 +198,8 @@ uca_net_camera_write (UcaCamera *camera,
         bytes_left -= written;
     }
 
-    handle_default_reply (priv->connection, UCA_NET_MESSAGE_WRITE, error);
+    handle_default_reply (connection, UCA_NET_MESSAGE_WRITE, error);
+    g_object_unref (connection);
 }
 
 static gboolean
@@ -196,6 +208,7 @@ uca_net_camera_grab (UcaCamera *camera,
                      GError **error)
 {
     UcaNetCameraPrivate *priv;
+    GSocketConnection *connection;
     GInputStream *input;
     GOutputStream *output;
     gsize bytes_left;
@@ -204,17 +217,19 @@ uca_net_camera_grab (UcaCamera *camera,
     g_return_val_if_fail (UCA_IS_NET_CAMERA (camera), FALSE);
     priv = UCA_NET_CAMERA_GET_PRIVATE (camera);
 
-    input = g_io_stream_get_input_stream (G_IO_STREAM (priv->connection));
-    output = g_io_stream_get_output_stream (G_IO_STREAM (priv->connection));
+    connection = connect_socket (priv, error);
+    input = g_io_stream_get_input_stream (G_IO_STREAM (connection));
+    output = g_io_stream_get_output_stream (G_IO_STREAM (connection));
     request.size = priv->size;
 
     /* request */
     if (!g_output_stream_write_all (output, &request, sizeof (request), NULL, NULL, error)) {
+        g_object_unref (connection);
         return FALSE;
     }
 
     /* error reply */
-    if (handle_default_reply (priv->connection, UCA_NET_MESSAGE_GRAB, error)) {
+    if (handle_default_reply (connection, UCA_NET_MESSAGE_GRAB, error)) {
         bytes_left = priv->size;
 
         while (bytes_left > 0) {
@@ -230,9 +245,11 @@ uca_net_camera_grab (UcaCamera *camera,
             bytes_left -= read;
         }
 
+        g_object_unref (connection);
         return TRUE;
     }
 
+    g_object_unref (connection);
     return FALSE;
 }
 
@@ -241,7 +258,7 @@ uca_net_camera_trigger (UcaCamera *camera,
                         GError **error)
 {
     g_return_if_fail (UCA_IS_NET_CAMERA (camera));
-    request_call (UCA_NET_CAMERA_GET_PRIVATE (camera)->connection, UCA_NET_MESSAGE_TRIGGER, error);
+    request_call (UCA_NET_CAMERA_GET_PRIVATE (camera), UCA_NET_MESSAGE_TRIGGER, error);
 }
 
 static gboolean
@@ -283,6 +300,7 @@ uca_net_camera_set_property (GObject *object,
                              GParamSpec *pspec)
 {
     UcaNetCameraPrivate *priv;
+    GSocketConnection *connection;
     const gchar *name;
     GError *error = NULL;
 
@@ -296,10 +314,13 @@ uca_net_camera_set_property (GObject *object,
     }
 
     /* handle remote props */
+    connection = connect_socket (priv, &error);
     name = g_param_spec_get_name (pspec);
 
-    if (!request_set_property (priv->connection, name, value, &error))
+    if (!request_set_property (connection, name, value, &error))
         g_warning ("Could not set property: %s", error->message);
+
+    g_object_unref (connection);
 }
 
 static gboolean
@@ -369,6 +390,7 @@ uca_net_camera_get_property (GObject *object,
                              GParamSpec *pspec)
 {
     UcaNetCameraPrivate *priv;
+    GSocketConnection *connection;
     const gchar *name;
     GError *error = NULL;
 
@@ -381,35 +403,19 @@ uca_net_camera_get_property (GObject *object,
     }
 
     /* handle remote props */
+    connection = connect_socket (priv, &error);
     name = g_param_spec_get_name (pspec);
 
-    if (!request_get_property (priv->connection, name, value, &error))
+    if (!request_get_property (connection, name, value, &error))
         g_warning ("Could not get property: %s", error->message);
+
+    g_object_unref (connection);
 }
 
 static void
 uca_net_camera_dispose (GObject *object)
 {
-    UcaNetCameraPrivate *priv;
-
-    priv = UCA_NET_CAMERA_GET_PRIVATE (object);
-
-    if (priv->connection != NULL) {
-        GOutputStream *output;
-        GError *error = NULL;
-        UcaNetMessageDefault request = { .type = UCA_NET_MESSAGE_CLOSE_CONNECTION };
-
-        output = g_io_stream_get_output_stream (G_IO_STREAM (priv->connection));
-
-        if (!g_output_stream_write_all (output, &request, sizeof (request), NULL, NULL, &error)) {
-            g_warning ("Could not close connection: %s", error->message);
-            g_error_free (error);
-        }
-
-        g_object_unref (priv->connection);
-    }
-
-    g_object_unref (priv->client);
+    g_object_unref (UCA_NET_CAMERA_GET_PRIVATE (object)->client);
     G_OBJECT_CLASS (uca_net_camera_parent_class)->dispose (object);
 }
 
@@ -516,6 +522,7 @@ static void
 uca_net_camera_constructed (GObject *object)
 {
     UcaNetCameraPrivate *priv;
+    GSocketConnection *connection;
 
     priv = UCA_NET_CAMERA_GET_PRIVATE (object);
 
@@ -526,13 +533,14 @@ uca_net_camera_constructed (GObject *object)
         priv->host = env != NULL ? g_strdup (env) : g_strdup ("localhost");
     }
 
-    priv->connection = g_socket_client_connect_to_host (priv->client, priv->host, UCA_NET_DEFAULT_PORT, NULL, &priv->construct_error);
+    connection = connect_socket (priv, &priv->construct_error);
 
-    if (priv->connection != NULL) {
+    if (connection != NULL) {
         /* ask for additional camera properties */
-        if (send_default_message (priv->connection, UCA_NET_MESSAGE_GET_PROPERTIES, &priv->construct_error))
-            read_get_properties_reply (object, g_io_stream_get_input_stream (G_IO_STREAM (priv->connection)),
-                                       &priv->construct_error);
+        if (send_default_message (connection, UCA_NET_MESSAGE_GET_PROPERTIES, &priv->construct_error))
+            read_get_properties_reply (object, g_io_stream_get_input_stream (G_IO_STREAM (connection)), &priv->construct_error);
+
+        g_object_unref (connection);
     }
 }
 
diff --git a/uca-net-protocol.h b/uca-net-protocol.h
index de05aac..4a1b5b6 100644
--- a/uca-net-protocol.h
+++ b/uca-net-protocol.h
@@ -15,7 +15,6 @@ typedef enum {
     UCA_NET_MESSAGE_TRIGGER,
     UCA_NET_MESSAGE_GRAB,
     UCA_NET_MESSAGE_WRITE,
-    UCA_NET_MESSAGE_CLOSE_CONNECTION,
 } UcaNetMessageType;
 
 typedef struct {
diff --git a/ucad.c b/ucad.c
index 4d46bca..b66124e 100644
--- a/ucad.c
+++ b/ucad.c
@@ -333,12 +333,14 @@ handle_write_request_cleanup:
     g_free (buffer);
 }
 
-static void
-serve_connection (GSocketConnection *connection, UcaCamera *camera)
+static gboolean
+run_callback (GSocketService *service, GSocketConnection *connection, GObject *source, gpointer user_data)
 {
     GInputStream *input;
+    UcaCamera *camera;
+    UcaNetMessageDefault *message;
     gchar *buffer;
-    gboolean active;
+    GError *error = NULL;
 
     HandlerTable table[] = {
         { UCA_NET_MESSAGE_GET_PROPERTIES,   handle_get_properties_request },
@@ -354,34 +356,23 @@ serve_connection (GSocketConnection *connection, UcaCamera *camera)
         { UCA_NET_MESSAGE_INVALID,          NULL }
     };
 
+    camera = UCA_CAMERA (user_data);
     buffer = g_malloc0 (4096);
     input = g_io_stream_get_input_stream (G_IO_STREAM (connection));
-    active = TRUE;
-
-    while (active) {
-        UcaNetMessageDefault *message;
-        GError *error = NULL;
 
-        /* looks dangerous */
-        g_input_stream_read (input, buffer, 4096, NULL, &error);
-        message = (UcaNetMessageDefault *) buffer;
+    /* looks dangerous */
+    g_input_stream_read (input, buffer, 4096, NULL, &error);
+    message = (UcaNetMessageDefault *) buffer;
 
 #if (GLIB_CHECK_VERSION (2, 36, 0))
-        if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_BROKEN_PIPE)) {
+    if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_BROKEN_PIPE)) {
 #else
-        if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_FAILED)) {
+    if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_FAILED)) {
 #endif
-            g_error_free (error);
-            error = NULL;
-            active = FALSE;
-            break;
-        }
-
-        if (message->type == UCA_NET_MESSAGE_CLOSE_CONNECTION) {
-            active = FALSE;
-            break;
-        }
-
+        g_error_free (error);
+        error = NULL;
+    }
+    else {
         for (guint i = 0; table[i].type != UCA_NET_MESSAGE_INVALID; i++) {
             if (table[i].type == message->type)
                 table[i].handler (connection, camera, buffer, &error);
@@ -390,30 +381,10 @@ serve_connection (GSocketConnection *connection, UcaCamera *camera)
         if (error != NULL) {
             g_warning ("Error handling requests: %s", error->message);
             g_error_free (error);
-            active = FALSE;
         }
     }
 
     g_free (buffer);
-}
-
-static gboolean
-run_callback (GSocketService *service, GSocketConnection *connection, GObject *source, gpointer user_data)
-{
-    GInetSocketAddress *sock_address;
-    GInetAddress *address;
-    gchar *address_string;
-
-    sock_address = G_INET_SOCKET_ADDRESS (g_socket_connection_get_remote_address (connection, NULL));
-    address = g_inet_socket_address_get_address (sock_address);
-    address_string = g_inet_address_to_string (address);
-    g_message ("Connection accepted from %s:%u", address_string, g_inet_socket_address_get_port (sock_address));
-
-    g_free (address_string);
-    g_object_unref (sock_address);
-
-    serve_connection (connection, UCA_CAMERA (user_data));
-    
     return FALSE;
 }