net.createServer 分片问题

Hello. I read your documentation, it is very detailed. I have a question. I followed the documentation to create a socket program, and found that when the message sent by the client is small, there is no problem, but when the content is large, the server receives it in pieces. The YYYY in the following code is printed multiple times. To combine the data received, it is the original message from the client. I would like to ask you how to combine the socket requests in pieces and then execute the dosomething() method.