Add all BENNC message types with unit tests

src/messages/subscribe.ts

@@ -0,0 +1,22 @@
+import { MessageTypes } from '../common'
+import { numberToUint16BE } from '../utilities/number'
+import { packOutgoingPacket } from './packet'
+
+const MESSAGE_TYPE = numberToUint16BE(MessageTypes.Subscribe)
+
+export interface SubscribeMessage {
+  messageType: number
+}
+
+/**
+ * Create an outgoing subscribe (0x0000) packet.
+ * @param properties The properties for the message.
+ * @returns An outgoing subscribe (0x0000) packet.
+ */
+export function packSubscribeMessage (properties: SubscribeMessage): Buffer {
+  const data = numberToUint16BE(properties.messageType)
+  return packOutgoingPacket({
+    messageType: MESSAGE_TYPE,
+    data: data
+  })
+}