INT 21 - DOS 3.1+ network - SET MACHINE NAME
AX = 5E01h
CH = 00h undefine name (make it invalid)
<> 0  define name
CL = name number
DS:DX -> 15-character blank-padded ASCIZ name

See also: 215E00

215E01CH00 - DOS 3.1+ network - SET MACHINE NAME