A decentralized network system, comprising: a plurality of normally unconnected nodes including a plurality of fixed nodes and a plurality of mobile nodes; wherein each fixed node includes a memory for storing messages and a communications port for transmitting and receiving messages and wherein each fixed node is associated with a device or location; wherein each mobile node includes a memory for storing messages, a processor for exchanging messages with fixed nodes in accordance with a predetermined relationship comprising rules for creating, storing and handling messages, and a communications port for transmitting and receiving messages, wherein the processor is responsive to a user input to generate a message; wherein the message is transmitted node (12, 20) by node (12, 20) across the network from a source node to a destination node which is not connected to the source node, through a sequence of message exchanges between nodes resulting from movement of mobile nodes and interactions of mobile nodes with fixed nodes; wherein the message is transmitted from a first fixed node to a second fixed node by movement of a mobile node from said first fixed node to said second fixed node; wherein the message comprises content; and characterised in that: the message comprises information representing the message's transmission status selected from the group of new, in transit, delivered and expired, each fixed node and/or each mobile node further comprises a message state machine for modifying the transmission status of the messages, and each message further comprises a unique identifier, pertaining to a destination node and/or an expiration time. a plurality of normally unconnected nodes including a plurality of fixed nodes and a plurality of mobile nodes; wherein each fixed node includes a memory for storing messages and a communications port for transmitting and receiving messages and wherein each fixed node is associated with a device or location; wherein each mobile node includes a memory for storing messages, a processor for exchanging messages with fixed nodes in accordance with a predetermined relationship comprising rules for creating, storing and handling messages, and a communications port for transmitting and receiving messages, wherein the processor is responsive to a user input to generate a message; wherein the message is transmitted node (12, 20) by node (12, 20) across the network from a source node to a destination node which is not connected to the source node, through a sequence of message exchanges between nodes resulting from movement of mobile nodes and interactions of mobile nodes with fixed nodes; wherein the message is transmitted from a first fixed node to a second fixed node by movement of a mobile node from said first fixed node to said second fixed node; the message comprises information representing the message's transmission status selected from the group of new, in transit, delivered and expired, each fixed node and/or each mobile node further comprises a message state machine for modifying the transmission status of the messages, and each message further comprises a unique identifier, pertaining to a destination node and/or an expiration time.