Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site umcp-cs.UUCP Path: utzoo!watmath!clyde!burl!ulysses!gatech!seismo!umcp-cs!chris From: chris@umcp-cs.UUCP (Chris Torek) Newsgroups: net.dcom Subject: Re: How and Why to build an Echo Host Message-ID: <2164@umcp-cs.UUCP> Date: Sat, 9-Nov-85 02:27:47 EST Article-I.D.: umcp-cs.2164 Posted: Sat Nov 9 02:27:47 1985 Date-Received: Sun, 10-Nov-85 08:43:27 EST References: <833@wdl1.UUCP> Organization: U of Maryland, Computer Science Dept., College Park, MD Lines: 15 It is surprisingly easy to build an Echo Host for 4.2 or 4.3 BSD. Try connecting to umd-echo: it is a poor underpowered 750 doing the IP packet turnaround in user code. Jim O'Toole wrote the `IP Magic Address' hacks we are using to implement this. Basically, it allows a raw socket to turn on a new IP address. The Ethernet ARP code is modified to respond to requests for the magic address; the inet input code is modified to accept packets destined for the magic address and hand them to the raw socket code; and the raw code knows to hand these only to the magic socket. (In case it is not in your host tables, umd-echo is 128.8.128.30.) -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251) UUCP: seismo!umcp-cs!chris CSNet: chris@umcp-cs ARPA: chris@mimsy.umd.edu