The input TCP component in node-red shows that the connection is connected and occasionally the data is not received. What's the solution?
You have done something wrong??? 
Seriously go read your post and think about how anyone, other than yourself, could possible answer your question. You haven't provided any kind of details at all.
what version of node-red and node.js?
what platform is NR runniing on?
What os is the platform using?
provide a copy of your flow
what contrib nodes are you using (i.e. node-red-contrib-xxxxx)
what is the device connecting via tcp?
what type of data is the device sending?
is the device hard wired or using a network?
Is the network wireless?
Those are just a few of the questions that pop up into my head.
Assuming Ethernet, use Wireshark to confirm data is being sent. My guess is your device is not sending data or your TCP node is not configured correctly.
As requested above, additional information is required. We aren't psychic 
Node-red version number V0.20.6
JS Version V10.16.0
On raspberry pie 3B + and running program on Linux operating system
Problem node is TCP in node, which occasionally receives no data; server written by JAVA, TCP in node program as the client, receives the data sent by server, and occasionally receives no data.
Data is HEX (hexadecimal), buffer
Using Router to Build Local Area Network for Wireless Communication
Node-red version number V0.20.6
JS Version V10.16.0
On raspberry pie 3B + and running program on Linux operating system
Problem node is TCP in node, which occasionally receives no data; server written by JAVA, TCP in node program as the client, receives the data sent by server, and occasionally receives no data.
Data is HEX (hexadecimal), buffer
Using Router to Build Local Area Network for Wireless Communication
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