INT 21 - LANtastic - SET MESSAGE SERVICE VECTOR
AX = 5FE3h
ES:BX -> FAR routine for processing network messages
Return: CF clear if successful
CF set on error
AX = error code
Notes:  handler must chain to previous handler as its first action
on invocation, ES:BX -> just-received message

See also: 215FE2

215FE3 - LANtastic - SET MESSAGE SERVICE VECTOR