Methods and systems for message forwarding and property notifications using electronic subscriptions

A messaging system is described in which subscription requests are transmitted over the Internet using Internet protocols such as extensions of HyperText Transport Protocol (HTTP). The subscription request may be for a wide variety of information from the remote device. For example, the subscription request might be for messages to be forwarded from the device as they are received. Also, the subscriptions could be for messages to be generated when a property value of the remote device has a predetermined characteristic. Such property values might include, for example, stock prices, inventory levels, online status, error codes, heart rates, and the like. The subscription request itself is a data structure representing a subscribe method identification, an address of the device containing the information, and an address of the device to which the information is to be forwarded. Optionally, the subscription request may also define the conditions under which a message is to be forwarded, or under which a property notification is to be sent.