java實現TCP通信

1.概述

通過ServerSocket與Socket實現的TCP的通信,這個例子配合了swing使用,其實作者之前發過一篇ServerSocker與Socket的通信,在這裏,這邊文章就是在這個例子上修改而成的.

其實原理很簡單的,就是一個服務端一個客戶端,服務端這邊創建好ServerSocket後,使用accept()堵塞一直等待客戶端發送socket.

好吧,不廢話了.進正題.

2.服務端

swing的部分就不說了,說一下主要操作.

(1)新建ServerSocket

ServerSocket serverSocket = null;
serverSocket = new ServerSocket(12345);//一個不被佔用的端口即可

構造方法的參數是端口,默認使用本地ip.
ServerSocket有三個構造方法.

ServerSocket(int port);
ServerSocket(int port,int backlog);
ServerSocker(int poer,int backlog,InetAddress ip);

詳情可以看這裏

(2)接收socket

Socket socket = serverSocket.accept();

返回一個Socket(),會一直等待,處於阻塞狀態.
一般設置一個while(true)循環接收.

(3)數據處理

使用DataInputStream與DataOutputStream:

DataInputStream inputStream = new DataInputStream(socket.getInputStream());
DataOutputStram outputStream = new DataOutputStream(socket.getOutputStream());

然後使用read與write方法即可.
注意關閉的時候要等輸入輸出完成後再一起關閉,就是說,不能這樣:

DataInputStream inputStream = new DataInputStream(socket.getInputStream());
String data = inputStream.readUTF();
inputStream.close();
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
outputStream.writeUTF("ok");
outputStream.close();

這樣的話getInputStream()沒有問題,但是到了getOutputStream()的時候就有問題了,會提示異常:

Socket is closed.
所以解決辦法就是等輸出完之後再一起關閉:

DataInputStream inputStream = new DataInputStream(socket.getInputStream());
String data = inputStream.readUTF();
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
outputStream.writeUTF("ok");
inputStream.close();//等輸出完成後再關閉
outputStream.close();

(4)完整代碼Server.java

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import javax.swing.*;

public class Server {
    public static void main(String[] args)
    {
        JFrame frame = new JFrame("Server");
        JPanel panel = new JPanel();
        JTextArea text = new JTextArea();

        panel.add(text);
        frame.setContentPane(panel);
        frame.setSize(600, 300);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        ServerSocket serverSocket = null;
        try
        {
            serverSocket = new ServerSocket(12345);
            while (true)
            {
                Socket socket = serverSocket.accept();
                DataInputStream inputStream = new DataInputStream(socket.getInputStream());
                text.setText(inputStream.readUTF());

                DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
                outputStream.writeUTF("ok");
                inputStream.close();
                outputStream.close();
                socket.close();
            }
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
        finally
        {
            try
            {
                serverSocket.close();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        }
    }
}

3.客戶端

客戶端的操作就是開啓一個Socket,再通過這個socket獲取對應的輸入輸出流就可以了.

(1)新建一個Socket

Socket socket = new Socket("127.0.0.1",12345);//這個端口與服務端的端口對應

Socket有三個構造方法:

Socket(InetAddress ip,int port);
Socket(String ip,int port);
Socket(InetAddress ip,int port,InetAddress localIp,int localPort);
Socket(String ip,int port,InetAddress localIp,int localPort);

詳情可以看這裏

(2)輸入輸出

同樣使用DataInputStream與DataOutputStream:

DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
DataInputStream inputStream = new DataInputStream(socket.getInputStream());

(3)完整代碼Client.java

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;

import javax.swing.*;
import java.awt.GridLayout;
public class Client
{
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        JTextArea text = new JTextArea();
        JButton send = new JButton();
        GridLayout layout = new GridLayout(2, 1, 0, 5);

        frame.setTitle("Client");
        frame.setVisible(true);
        frame.setLocationRelativeTo(null);
        frame.setSize(600, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(layout);

        frame.add(text);
        frame.add(send);
        send.setText("send");
        send.addActionListener(v ->
        {
            try
            {
                String host = "127.0.0.1";
                int port = 12345;
                Socket socket = new Socket(host, port);
                DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
                outputStream.writeUTF(text.getText());

                DataInputStream inputStream = new DataInputStream(socket.getInputStream());
                text.setText(inputStream.readUTF());
                outputStream.close();
                inputStream.close();
                socket.close();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
        });
    }
}

4.測試

先開啓服務端,再開啓客戶端,這裏設置了服務端返回給客戶端的信息爲"ok".