Summary of Java communication API (3) How to use SocketChannel

1. 1. Introduction

This time, I will briefly summarize how to use SocketChannel. Please refer to the flow as follows.

--Client

1. Connect the server via SocketChannel

2. Prepare a data buffer and write / read to the server

3. Close Socket Channel

--Server

1. Bind iP address and port

2. Get an instance of SocketChannel with the ServerSocketChannelImpl.accept () method

3. Prepare a data buffer and write / read to the client

4. Close SocketChannel and ServerSocketChannel

Then, let's make a communication demo of the client and the server from here.

2. client

The source code is as follows.

package socketchannel;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;

public class WebClient {
  public static void main(String[] args) throws IOException {

//1. Let's create a SocketChannel instance with the SocketChannel open () method SocketChannel socketChannel = SocketChannel.open();

// 2. Connect to the server socketChannel.connect(new InetSocketAddress("127.0.0.1", 3333));

// 3. Prepare the data to be sent to the server ByteBuffer writeBuffer = ByteBuffer.allocate(128); writeBuffer.put("hello WebServer this is from WebClient".getBytes()); writeBuffer.flip(); socketChannel.write(writeBuffer); ByteBuffer readBuffer = ByteBuffer.allocate(128); socketChannel.read(readBuffer); StringBuilder stringBuffer=new StringBuilder();

// 4. Receive data from the server readBuffer.flip(); while (readBuffer.hasRemaining()) { stringBuffer.append((char) readBuffer.get()); } System.out.println ("Message from server:" + stringBuffer); socketChannel.close(); } }

3. 3. server

The source code on the server side is as follows.

package socketchannel;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;

public class WebServer {
public static void main(String args[]) throws IOException {
    try {

// 1. Create an instance of ServerSocketChannel with the open () method of ServerSocketChannel ServerSocketChannel ssc = ServerSocketChannel.open();

//2. Bind ip and port ssc.socket().bind(new InetSocketAddress("127.0.0.1", 3333));

//ServerSocketChannelImplのaccept()メソッドでSocketChannelインスタンスをもらってクライアントへの書き読み SocketChannel socketChannel = ssc.accept();

// 3. Prepare the data to export ByteBuffer writeBuffer = ByteBuffer.allocate(128); writeBuffer.put("hello WebClient this is from WebServer".getBytes()); writeBuffer.flip(); socketChannel.write(writeBuffer); ByteBuffer readBuffer = ByteBuffer.allocate(128);

////4. Prepare the data to read socketChannel.read(readBuffer); StringBuilder stringBuffer=new StringBuilder();

        readBuffer.flip();
        while (readBuffer.hasRemaining()) {
            stringBuffer.append((char) readBuffer.get());
        }

System.out.println ("Receive data from client:" + stringBuffer); socketChannel.close(); ssc.close(); } catch (IOException e) { e.printStackTrace(); } } }

Well, if you run the above demo and it works, the result will be:

4. Finally

Thank you for reading to the end.