A user terminal emulation server maintains a database identifying network addresses, UI capabilities, and communication protocols of I/O user devices. Communication sessions are established between a user terminal emulation application and a network entity and I/O user devices proximately located to a user and provide a combined I/O user interface. Delay profiles are determined between the application and the I/O user devices. A downlink flow from the network entity is split into a plurality of downlink flow components assigned to the I/O user devices. For each of the downlink flow components, the server formats the component for transmission to the assigned I/O user device, initiates transmission of the formatted downlink flow component to the assigned I/O user device, and controls timing for when the formatted downlink flow component is transmitted to the assigned I/O user device based on the delay profile associated with the assigned I/O user device.