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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