The present invention extends to methods, systems, and computer program products for controlling the transfer of terminal server data. In some embodiments, contending request to send terminal server data are resolved by a flow control module situated between a terminal server protocol and a transport/network protocol. The flow control module utilizes channel priorities along with amounts of previously sent data per channel to determine how to distribute bandwidth in a relatively controlled manner between contending channels. The flow control module can be configured to intercept communication between terminal server protocol and a transport/network protocol to facilitate bandwidth distribution. In other embodiments, data is simultaneously sent over multiple channels of terminal server connection. A first write operation obtains a lock on a corresponding channel but the channel lock does not prevent write operations on other channels.