What is the use of 127.0.0.1, "localhost" ?

[Espronceda]

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I know we can use localhost to make sure the TCPIP stack is properly
installed, by using "ping 127.0.0.1".
But I suspect it is there for something else ..
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By example, using Sysinternals "TCPVIEW" tool, I see that FIREFOX
opens a connection between 127.0.0.1:3054 and 127.0.0.1:3053 ...
Dont know the use it has but this is not impotant now.
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My question is : WHAT OTHER USES DOES 127.0.0.1 HAVE ?
Some ideas/samples, any pointer ...
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Thanks.
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