[Dubbo-936]fix The nc command is unstable in the dubbo startup script #936

[CrazyHZM]

What is the purpose of the change

fix #936

Brief changelog

XXXXX

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #3375 into master will increase coverage by 0.08%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #3375      +/-   ##
============================================
+ Coverage     63.77%   63.85%   +0.08%     
  Complexity       71       71              
============================================
  Files           661      661              
  Lines         28519    28519              
  Branches       4797     4797              
============================================
+ Hits          18187    18210      +23     
+ Misses         8117     8098      -19     
+ Partials       2215     2211       -4

Impacted Files	Coverage Δ	Complexity Δ
.../remoting/transport/netty4/NettyClientHandler.java	61.4% <0%> (-7.02%)	0% <0%> (ø)
.../apache/dubbo/remoting/transport/AbstractPeer.java	58.69% <0%> (-4.35%)	0% <0%> (ø)
...onfig/spring/extension/SpringExtensionFactory.java	78.04% <0%> (-2.44%)	0% <0%> (ø)
...pache/dubbo/registry/support/AbstractRegistry.java	79.52% <0%> (-0.79%)	0% <0%> (ø)
...dubbo/remoting/exchange/support/DefaultFuture.java	72.97% <0%> (+1.35%)	0% <0%> (ø)	⬇️
...exchange/support/header/HeaderExchangeHandler.java	58.13% <0%> (+2.32%)	0% <0%> (ø)	⬇️
...bo/rpc/cluster/support/FailbackClusterInvoker.java	70.49% <0%> (+3.27%)	0% <0%> (ø)	⬇️
...e/dubbo/remoting/transport/netty/NettyChannel.java	62.35% <0%> (+4.7%)	0% <0%> (ø)	⬇️
.../org/apache/dubbo/remoting/ExecutionException.java	21.05% <0%> (+5.26%)	0% <0%> (ø)	⬇️
...ng/exchange/support/header/HeartbeatTimerTask.java	78.94% <0%> (+5.26%)	0% <0%> (ø)	⬇️
... and 6 more

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[ralf0131]

Would you please update the title into English?

[CrazyHZM]

Would you please update the title into English?
I have modified it.

[beiwei30]

I believe nc can be more stable once we increase the interval, for example: nc -i 2 or some other greater value.

If we want to use telnet to replace nc, at least we should change the command to:

COUNT=`(sleep 1; echo -e '\n'; sleep 1; echo status; sleep 1)| telnet $SERVER_HOST $SERVER_PORT | grep -c OK`