Telnet protocol: the standard protocol and main method of remote login service

Use telnet to test the connectivity of Linux/Windows ports

The telnet contract is a member of the TCP/IP contract family and is the standard contract and main form of Internet remote login service. It provides users with the ability to complete remote host work on their local computer. Use the telnet program linux telnet port on the end user's laptop and use it to connect to the server. End users can enter commands into the telnet program, which will run on the server linux telnet port as if they were entered directly on the server's console. Therefore, the port connectivity can be tested through telnet.

Test whether the port is moved under Linux system

Command format:

telnet ip port

ip is the ip address of the test host

port is the port

For example:

telnet 127.0.0.1 6379

127.0.0.1 is the local loopback address linux forum, mainly used for testing. 6379 is the default port of the Redis service.

If there is a port for telnet connection, the following content will appear:

Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.

At this time, follow the prompts for the linux serial port driver. Press Ctrl+] to call out the telnet command line. After getting down the telnet command line, you can execute the telnet command. For example, to exit telnet, quit

^]
telnet> quit
Connection closed.

If the telnet connection does not exist, the following content will appear:

Trying 127.0.0.1...

Press Ctrl+C to end.

【Supplement】Test the network telecommunications status under Windows system

Detecting network telecommunications status under Windows is very simple:

Win+R opens the cmd command window, command format:

ping ip

If the network telecommunications is used, the picture on the right will appear

测试Windows系统下端口是否连通

命令格式：

telnet ip port

如：

telnet 127.0.0.1 6379

假如连通会直接步入telnet，退出方式同Linux

假如端口未连通，提示如下：

正在连接127.0.0.1... 无法打开到主机的连接。 在端口 6379：连接失败

不仅用telnet来测试端口的连通性，还有wget、ssh、crul方式，可自行查询用法。

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