Network connection verification

Network connection verification method

This article mainly summarizes the methods of centralized troubleshooting when the address of the access partner is not available during normal development . The following are in linux Command operation in environment .

IP Address classification

• A class ：1.0.0.0-127.255.255.255
• B class ：128.0.0.0-191.255.255.255
• C class ：192.0.0.0-223.255.255.255
• D Class address is used in IP Network Multicast ( multicasting , Also known as Multichannel broadcasting ).D Before class address 4 The position is constant 1110 , Before presetting 3 Position as 1 signify D Class address starts at 128+64+32 be equal to 224. The first 4 Position as 0 signify D The maximum value of the class address is 128+64+32+8+4+2+1 by 239, therefore D class The address space ranges from 224.0.0.0 To 239. 255. 255.254.
• E Class address reserved for research . therefore Internet There is nothing available on E Class address .E Before class address 4 The position is constant 1, So the valid address range is 240.0.0.0 to 255.255.255.255.
  D Classes and E Class is reserved , Out of commission .

Intranet ip, Public network ip And export ip The difference between

This machine IP（ Intranet ip） It's you ( Intranet ) Medium IP, Can only be used in a LAN , In the Internet and Internet cafes, you need to access your local computer IP, Generally, it cannot be opened , This is through your exit IP To visit , And you must map the port on the router to your computer to access , exit IP It is usually called the public network IP.

View the exit ip The way

• curl cip.cc
  return ip And operator information
• curl ifconfig.me or curl ident.me
  Returns a single ip
• curl ipinfo.io

Test whether the network is smooth

telnet There are only two ways to test whether the network is smooth , But either way, you must add ports , Otherwise, it will fail , When using domain name , The corresponding port is generally 80 perhaps 443.

• telnet ip port
• telnet domain name port
  for example ：telnet www.baidu.com 443