In a method of performing the asynchronous delivery of messages from a server to a client, the server receives the messages for the client from a message source. The server and client communicate over a packet network using an asymmetric protocol that requires request messages to be originated from the client to the server. At least one request message is sent in advance from the client to the server, and these request messages are stored at the server. When the server receives a message for the client from the message source, it forwards the message to the client as a response to a stored request message.