The present invention provides for a virtual serial port (VSP) situated between a serial port in a mobile electronic device, applications that require a serial port connection handle, and other applications that require command-mode access to the serial port. Data-communication applications (e.g. web browsing, e-mail, etc.) connect to the serial port through the VSP. The VSP creates a virtual connection handle that is returned to the application. Command-mode requests (e.g., short messaging requests) are received by the hardware abstraction layer, translated into command-mode messages (e.g., AT commands) and placed in a queue. The VSP multiplexes the serial port between the currently-open data communication session (data-mode) and command-mode messages by periodically suspending the currently-open connection and processing one or more command-mode messages that are in the queue. A buffer continually stores incoming data while the data communication session is suspended. The VSP uses a heuristic calculation to determine the maximum time interval for which the data-communication session can be interrupted. The heuristic calculation takes a percentage of a time-quantum (e.g. 0.5 seconds) based upon the ratio of an average bit rate for air communication (e.g. 7000 bits/sec) and a bit rate for the serial port (e.g. 152,000 bits/sec). This ensures that data-communications are not interrupted for a time interval long enough to result in lost data-packets. The parameter for the time quantum and other parameters may be statically or dynamically adjusted to account for a finite buffer size in the hardware.
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