When you connect to Tomcat, you cannot enter it again after you enter telnet localhost 8080

When you first touch a server, you typically create a local mini-server that is used today when you use Apache Tomcat to access a custom resource under WebApps in the server under command line: first open a command-line window and enter telnet localhost 8080, pop-up another interface, but there are the following phenomena can not be entered,

At first I thought it was the local echo function did not open, and then according to the online prompt, opened the Echo function, but the problem still exists, later, found a solution:

In the new command-line window, after you enter telnet localhost 8080, press CTRL +] (two keys in English), and then press ENTER, the input is displayed.

Add: After entering get/myapp/1.html http/1.1, hit Enter, then enter host:
     At this point, you have to tap the two times to get the requested data.