The construction of short message UDP packet failed.

The key to solve the problem: First, only one socket is established to send and receive data, and each time you click Connect, it is newly created, while the socket of the same port will not be newly created or closed before clicking Disconnect, so that the port resolved by the PC-side service program will not change before disconnecting, which can solve the two problems mentioned in the previous paragraph. Second, the PC-side service program should have parsing function, and it is best to use what I provide. By the way, if the socket of the same port is created again when it is not closed, the program will automatically quit.