"Renegotiation" agreement

Agreement is a kind of agreement , But for socket api The data in the socket is transmitted through strings , So if we want to transfer in a structured data , How to operate it ？

Online calculator

If we want to specify a calculator , Then the client should send two data and an operation symbol to the server , The server will send the final data to the client after analysis and calculation .

for example ： We need to specify an adder , Then the client should send two data and one to the server “+” Symbol , So for the server , He must have one of his own agreement , This agreement is the agreed plan , It is agreed that when the client requests the server , How data should be sent , How the data will eventually be returned , Only such operations , The client can get the results that customers want .

Agreed scheme

for example ： We're going to make an adder , Then we should have the following agreement
Appointment one ：

• The data sent is in order , And an addition operator between two numbers . for example ：“1+2”.
• The data sent must be an integer , Operator must be +.
• There are no spaces between numbers and operators .

Agreement II ：

• The data sent does not need to be sent in sequence , Use the structure to package .
• The data sent must be an integer , Operator must be +.

It's just a part of the agreement , Because we don't need many conventions to implement an adder .
Be careful ： Whether it is agreement one or agreement two , Their ultimate goal is to create a unified event （ For one thing ）, That is to let the customer send something , The server can know how to correctly handle the incoming data （ That is, the server can correctly parse ）.

Simple implementation of addition server

For the implementation of adder , We use a structure to send data , Because for the structure , It can separate data from operators , It makes it very easy to parse data and operators .
Encapsulates a socket class for an addition server , as follows ：

The server implementation is as follows ：

The implementation of the client is as follows :

Can see , During the transmission of information , Using a structure , Because the structure can directly separate the data and symbols we want to transfer , It can make the server better to parse , This is what serialization and deserialization do .

Serialization and deserialization

Above we mentioned serialization and deserialization , So what exactly do they mean ？

1. serialize ： The process of converting an object into a sequence of bytes .
2. Deserialization ： The process of restoring a sequence of bytes to objects .

To put it bluntly , Serialization and deserialization are just like a rule , The server can receive data , And correctly analyze these data , But they also have some important functions ：

• serialize ： Organize multiple objects in a specified format into binary data strings that can be stored persistently or transmitted .（ Ensure the integrity of the object , The ordered byte stream is used to prevent transmission on the network or storage in local files ）
• Deserialization ： The binary data string , Multiple data objects can be parsed according to the specified format .

Be careful ： For serialized forms , He has a consideration

• Transmission performance ： The serialized binary data string should be as short as possible .
• Analytical performance ： The simpler the process of serialization and deserialization, the better .

Above we use the structure , Because according to the structural characteristics of the structure , The assignment of member variables can realize the organization of data in memory . But he has shortcomings , Because for different platforms , The use of bit segments may be inconsistent , Byte alignment may also be inconsistent .

3. Advantages of serialization ：

• Keep objects permanently ： The objects are stored on the hard disk in the form of binary sequence , It can not only reduce the space , And even when the virtual machine is interrupted for some reason , The sequence on the hard disk will not be affected , After the next boot, the object can still be parsed according to deserialization .
• Objects serialized as byte streams can be transmitted over the network .
• Objects can be passed between processes through serialization .