title: Why doesn't ::1 match 127.0.0.1?
body: <p>The loopback IP address in IPv6 format is:
  0000:0000: <strong>0000:0000</strong>: 0000:0000: <strong>0000:0001</strong></p>
  
  <p>which is shortened to:
  0:0: <strong>0:0</strong>: 0:0: <strong>0:1</strong></p>
  
  <p>which is then shortened to (keep last 2 words, ie. 4 bytes, to match IPv4):
  <strong>:0:1</strong> (But I still don't know why it's double colons instead of single colon before 1, maybe for implying that there are 4 bytes here)</p>
  
  <p>and simplified as:
  <strong>::1</strong></p>
  
  <p>Expand ::1 into IPv4 format, it is:
  <strong>0.0.0.1</strong></p>
  
  <p>But this is not the same as <strong>127.0.0.1</strong>, where's the number 127?</p>