A proxy computer of a network can receive incoming telephony messages from one or more computers outside of the network and proxy them to computers within the network. Similarly, the proxy computer can receive outgoing telephony messages from within the network and proxy them to computers outside of the network. To set up inbound calls, a proxy program on the proxy computer looks for the presence of an alias in the call signaling messages, references a data structure to determine which computer on the network is associated with the alias, and proxies the call signaling and control messages between the callee computer and the calling computer based on the association, thereby creating a logical connection between the calling computer and the callee computer.