[Socket communication (Java)] Impressions of implementing Socket communication in practice for the first time

Since I had the opportunity to implement Socket communication in practice for the first time, I will make a note of my impressions and technology used. When I was studying by myself in the past, I didn't get it right, but I was able to experience it by looking at the data specifications and implementing it.

1. Socket communication overview

It seems that there are two types, server socket and client socket, but this time I used only the client socket. The impression was that there was a Java Socket API, but in the end, it was a byte stream exchange. The data specification also said something like "Data A: xxx to 4 bytes".

I referred to the following articles. @ Hyman1993 Summary of Java communication API (1) How to use Socket @Gin About TCP stream communication breaks / breaks

2. Byte order

There was a statement in the design document that "data is stored in little endian". For me, who is a beginner of Socket communication, it was a mess.

I referred to the article by @mikanbako. Byte order must be reset to duplicate ByteBuffer

2.1. There are 2 points.

--In order to process the read data, it is necessary to convert each byte array specified in the data specifications into a numerical value or a character string. --If the data is little endian, you need to specify the little endian when replicating to the ByteBuffer class. Ex. byteBuffer.order(ByteOrder.LITTLE_ENDIAN)

2.2. Excerpt from the article


import java.nio.ByteBuffer;
import java.nio.ByteOrder;

public class LittleEndianSample {
    public static final void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(Short.BYTES);

        //Little endian 16-bit integer. The low byte is 0x11 and the high byte is 0x22.
            .put((byte) 0x11)
            .put((byte) 0x22)

        System.out.printf("0x%x\n", buffer.getShort());

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