If you control both ends, either use the alread mentioned "S>" or "S<" or the network versions "n" and "v" (see perldoc -f pack).

    s  A signed short (16-bit) value.
    S  An unsigned short value.
    n  An unsigned short (16-bit) in "network" (big-endian) order.
    v  An unsigned short (16-bit) in "VAX" (little-endian) order.
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I made an overview of those pack results here for one of my talks.