Implement Keep Alive messages.

src/requests/keepalive.cr

@@ -0,0 +1,11 @@
+class DNSManager::Request
+	IPC::JSON.message KeepAlive, 250 do
+		def initialize()
+		end
+
+		def handle(dnsmanagerd : DNSManager::Service, event : IPC::Event) : IPC::JSON
+			Response::KeepAlive.new
+		end
+	end
+	DNSManager.requests << KeepAlive
+end

src/responses/keepalive.cr

@@ -0,0 +1,7 @@
+class DNSManager::Response
+	IPC::JSON.message KeepAlive, 250 do
+		def initialize()
+		end
+	end
+	DNSManager.responses << KeepAlive
+end