What is the difference between 127 0 0 1 and localhost

Question

Assuming the following is defined in     hosts   127 0 0 1 localhost   What  if any  are the actual differences between using 127 0 0 1 and localhost as the server name  especially when hitting processes running locally that are listening for connections

User · Answer

some applications will treat  localhost  specially   the mysql client will treat localhost as a request to connect to the local unix domain socket instead of using tcp to connect to the server on 127 0 0 1   This may be faster  and may be in a different authentication zone   I don t know of other apps that treat localhost differently than 127 0 0 1  but there probably are some

User · Answer

Well  by IP is faster   Basically  when you call by server name  it is converted to original IP    But it would be difficult to memorize an IP  for this reason the domain name was created    Personally I use http   localhost instead of http   127 0 0 1 or http   username

User · Answer

Well  the most likely difference is that you still have to do an actual lookup of localhost somewhere   If you use 127 0 0 1  then  intelligent  software will just turn that directly into an IP address and use it  Some implementations of gethostbyname will detect the dotted format  and presumably the equivalent IPv6 format  and not do a lookup at all   Otherwise  the name has to be resolved  And there s no guarantee that your hosts file will actually be used for that resolution  first  or at all  so localhost may become a totally different IP address   By that I mean that  on some systems  a local hosts file can be bypassed  The host conf file controls this on Linux  and many other Unices

User · Answer

There is nothing different  One is easier to remember than the other  Generally  you define a name to associate with an IP address  You don t have to specify localhost for 127 0 0 1  you could specify any name you want

User · Answer

The main difference is that the connection can be made via Unix Domain Socket  as stated here  localhost vs  127 0 0 1

User · Answer

Wikipedia sums this up well      On modern computer systems  localhost as a hostname translates to an IPv4 address in the 127 0 0 0 8  loopback  net block  usually 127 0 0 1  or   1 in IPv6    The only difference is that it would be looking up in the DNS for the system what localhost resolves to  This lookup is really  really quick  For instance  to get to stackoverflow com you typed in that to the address bar  or used a bookmarklet that pointed here   Either way  you got here through a hostname  localhost provides a similar functionality

[sockets] What is the difference between 127.0.0.1 and localhost

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