网络编程的坑：Java网络通信实例

原创 Bertha 。 2024-10-20 04:30 29阅读 0赞

在网络编程中，Java语言提供了一套完整的API来实现网络通信。以下是一个简单的Java网络通信实例，包括客户端和服务器端：

1. **客户端**（建立连接发送请求）：
```java
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.Socket;

public class Client {
    public static void main(String[] args) {
        // 创建Socket对象
        Socket socket = new Socket("localhost", 8080); // "localhost"是服务器的IP地址

// 获取输出流，用于发送数据
        OutputStream outputStream = socket.getOutputStream();

// 发送GET请求（假设要访问的URL为"/test"）
        String request = "GET /test HTTP/1.1\r\n" +
                "Host: localhost\r\n" +
                "\r\n";
        outputStream.write(request.getBytes());

// 接收服务器响应
        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream())));

String responseLine;
        StringBuilder responseContent = new StringBuilder();

while ((responseLine = br.readLine()) != null) {
            int index = responseLine.indexOf(":", 5); // "http_code"字段的位置
            if (index != -1) {
                responseContent.append(responseLine.substring(0, index))).append("\r\n");
            } else {
                responseContent.append(responseLine).append("\r\n");
            }
        }

System.out.println("Server Response:");
        System.out.println(responseContent.toString());

// 关闭Socket
        socket.close();
    }
}
```

2. **服务器端**（接收请求响应）：
```java
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    public static void main(String[] args) {
        // 创建ServerSocket对象，监听8080端口
        try (ServerSocket serverSocket = new ServerSocket(8080))) {
            System.out.println("Server is listening on port 8080...");

// 接收客户端连接
            Socket socket = serverSocket.accept();

System.out.println("Client connected from IP: " + socket.getInetAddress().getHostAddress()));

BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()))));
            StringBuilder responseContent = new StringBuilder();

String requestLine;
            while ((requestLine = in.readLine()) != null) {
                if (requestLine.startsWith("GET /")) && !requestLine.contains("HTTP_10")) { // 检查是否为GET请求
                    int index = requestLine.indexOf(" ", 6); // "query"字段的位置
                    if (index != -1) {
                        responseContent.append(requestLine.substring(0, index))).append("\r\n");
                        String query = requestLine.substring(index + 2).trim(); // 获取查询参数

// 根据查询参数生成响应内容
                        responseContent.append("HTTP/1.1 200 OK\r\n").append("\r\n").append("Content-Type: text/plain\r\n").append("\r\n");
                        if (query != null && !query.isEmpty()) { // 如果有查询参数，添加到响应中
                            responseContent.append("Query parameters: ").append(query).append("\r\n");
                        }
                    } else {
                        responseContent.append(requestLine).append("\r\n");
                    }
                } else {
                    System.out.println("Invalid request line: " + requestLine));
                    break;
                }
            }

// 向客户端发送响应内容
            socket.getOutputStream().write(responseContent.toString().getBytes()));

// 关闭Socket连接
            socket.close();

} catch (Exception e) {
            System.err.println("Error occurred while server is running: " + e.getMessage());
            e.printStackTrace();
            try { // 如果发生异常，尝试关闭ServerSocket
                serverSocket.close();
            } catch (Exception ex) {
                System.err.println("Error occurred while closing ServerSocket: " + ex.getMessage());
                ex.printStackTrace();
            }
        }

}
}
```

以上代码示例涵盖了客户端如何发送GET请求和服务器端如何接收并响应这些请求。注意，实际生产环境中需要处理更多边界情况和错误。