server: support reading back channels (#597) (#777)

examples/proxy-backchannel/main.go

@@ -0,0 +1,24 @@
+package main
+
+import "log"
+
+// This example shows how to
+// 1. create a server that serves a single stream.
+// 2. create a client, that reads an existing stream from another server or camera, containing a back channel.
+// 3. route the stream from the client to the server, and from the server to all connected readers.
+// 4. route the back channel from connected readers to the server, and from the server to the client.
+
+func main() {
+	// allocate the server.
+	s := &server{}
+	s.initialize()
+
+	// allocate the client.
+	// allow client to use the server.
+	c := &client{server: s}
+	c.initialize()
+
+	// start server and wait until a fatal error
+	log.Printf("server is ready on %s", s.server.RTSPAddress)
+	panic(s.server.StartAndWait())
+}