Systems and methods are described for delivering messages from one or more service hosts to clients via a network. A first request identifying the client is received at the message server, and a connection is established and maintained between the message server and the client in response to the first request. When a subsequent request that identifies the client is received from the service host, a message is transmitted from the message server to the client over the previously-established connection. The methods and techniques may be used, for example, to provide messages from various services to placeshifting devices or other clients communicating via the network.