Kronos ir right. MiamiDX is no longer available retail. You'd have to get a used copy. The author of MiamiDX can no longer issue registration keys as his 1200's (it was a 1200 right) hard drive died with all his registration records and key generation software... Besides, he now works for Rebol and doesn't seem to have much interest in the Amiga...
But it sure is one hell of a TCP/IP stack.