教你怎么用java实现客户端与服务器一问一答

如何用Java实现客户端与服务器一问一答

1. 建立TCP连接

1. 客户端调用Socket类的构造方法建立与服务器端的连接。在构造方法中需要传入服务器端的IP地址和端口号，示例代码如下：

java
String serverHost = "127.0.0.1"; // 服务器IP地址
int serverPort = 8888; // 服务器端口号
Socket socket = null;
try {
socket = new Socket(serverHost, serverPort);
} catch (IOException e) {
e.printStackTrace();
}

1. 服务器端通过调用ServerSocket类的构造方法监听指定的端口号。示例代码如下：

java
int port = 8888; // 监听端口号
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(port);
} catch (IOException e) {
e.printStackTrace();
}

2. 通过Input/OutputStream进行读写操作

在建立了TCP连接之后，客户端与服务器端可以通过流对象进行数据的传输。

1. 客户端可以使用socket对象的getOutputStream()方法获取输出流，通过输出流将数据发送给服务器端。示例代码如下：

java
OutputStream outputStream = socket.getOutputStream();
String message = "Hello, server!";
outputStream.write(message.getBytes());

1. 服务器端可以使用Socket类的getInputStream()方法获取输入流，通过输入流获取客户端发送的数据。示例代码如下：

java
InputStream inputStream;
try {
inputStream = socket.getInputStream();
byte[] bytes = new byte[1024];
int len;
StringBuilder sb = new StringBuilder();
while ((len = inputStream.read(bytes)) != -1) {
sb.append(new String(bytes, 0, len, StandardCharsets.UTF_8));
}
System.out.println("Message from client: " + sb);
} catch (IOException e) {
e.printStackTrace();
}

3. 示例1：客户端发送消息给服务端

在这个示例中，客户端将用户输入的字符串发送给服务器，服务器端将收到的字符串原样发送回客户端。

客户端代码

import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.nio.charset.StandardCharsets;
import java.util.Scanner;

public class Client {

    public static void main(String[] args) {
        String serverHost = "127.0.0.1";
        int serverPort = 8888;
        Socket socket = null;
        try {
            socket = new Socket(serverHost, serverPort);
            System.out.println("Connect to server: " + serverHost + ":" + serverPort);
            OutputStream outputStream = socket.getOutputStream();
            Scanner scanner = new Scanner(System.in);
            while (true) {
                System.out.print("Input message: ");
                String message = scanner.nextLine();
                outputStream.write(message.getBytes(StandardCharsets.UTF_8));
                if ("bye".equalsIgnoreCase(message)) {
                    break;
                }
            }
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (socket != null) {
                    socket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

服务器端代码

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;

public class Server {

    public static void main(String[] args) {
        int port = 8888;
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(port);
            System.out.println("Server listening on port " + port);
            while (true) {
                Socket socket = serverSocket.accept();
                System.out.println("New connection accepted: " + socket.getInetAddress() + ":" + socket.getPort());
                InputStream inputStream = socket.getInputStream();
                OutputStream outputStream = socket.getOutputStream();
                byte[] bytes = new byte[1024];
                int len;
                while ((len = inputStream.read(bytes)) != -1) {
                    String message = new String(bytes, 0, len, StandardCharsets.UTF_8);
                    System.out.println("Message from client: " + message);
                    outputStream.write(message.getBytes(StandardCharsets.UTF_8));
                }
                inputStream.close();
                outputStream.close();
                socket.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (serverSocket != null) {
                    serverSocket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

4. 示例2：服务器向客户端发送消息

在这个示例中，客户端连接服务器后，服务器向客户端发送消息。

客户端代码

import java.io.IOException;
import java.io.InputStream;
import java.net.Socket;
import java.nio.charset.StandardCharsets;

public class Client {

    public static void main(String[] args) {
        String serverHost = "127.0.0.1";
        int serverPort = 8888;
        Socket socket = null;
        try {
            socket = new Socket(serverHost, serverPort);
            System.out.println("Connect to server: " + serverHost + ":" + serverPort);
            InputStream inputStream = socket.getInputStream();
            byte[] bytes = new byte[1024];
            int len = inputStream.read(bytes);
            String message = new String(bytes, 0, len, StandardCharsets.UTF_8);
            System.out.println("Message from server: " + message);
            inputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (socket != null) {
                    socket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

服务器端代码

import java.io.IOException;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.StandardCharsets;

public class Server {

    public static void main(String[] args) {
        int port = 8888;
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(port);
            System.out.println("Server listening on port " + port);
            while (true) {
                Socket socket = serverSocket.accept();
                System.out.println("New connection accepted: " + socket.getInetAddress() + ":" + socket.getPort());
                OutputStream outputStream = socket.getOutputStream();
                String message = "Welcome to the server!";
                outputStream.write(message.getBytes(StandardCharsets.UTF_8));
                outputStream.close();
                socket.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (serverSocket != null) {
                    serverSocket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

以上就是用Java实现客户端与服务器一问一答的教程了。