java - 套接字客户端永远阻塞

Question

我正在用 Java 编写套接字客户端。在程序中，我想从服务器获取信息。当服务器收到“GET_LIGHTS”命令时，它会以 JSON 格式发回数据。

但在我的代码中，bw.write() 和 bw.flush() 在 socket.close() 之前不起作用.因此，BufferedReader 对象未就绪:br.ready() 返回 false。

我的代码有什么错误吗？

客户端代码如下所示。

package monitor;

import java.io.*;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.ArrayList;

public class SocketClient {
    static private int port;
    static private String hostName;
    private Socket socket;

    public SocketClient(String host, int port) {
        this.hostName = host;
        this.port = port;
    }

    // get lights by JSON
    public void getLights() {
        try {
            // generate socket
            InetSocketAddress endpoint = new InetSocketAddress(hostName, port);
            socket = new Socket();
            socket.connect(endpoint);

            // setting
            OutputStreamWriter out = new OutputStreamWriter(socket.getOutputStream());
            BufferedWriter bw = new BufferedWriter(out);

            InputStreamReader in = new InputStreamReader(socket.getInputStream());
            BufferedReader br = new BufferedReader(in);

            // send command
            bw.write("GET_LIGHTS");
            bw.flush();

            // receive message from server
            System.out.println(br.readLine());

            socket.close();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void initLights(ArrayList<Light> lights) {
        getLights();
    }

}

编辑:

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;

public class SocketServer extends Thread{
    static final int PORT = 44344;
    static private ILS ils;
    private ServerSocket serverSocket;
    private Socket socket;

    public SocketServer(ILS ils) {
        this.ils = ils;
    }
    @Override
    public void run() {
        serverSocket = null;
        System.out.println("Server: listening");

        try {
            serverSocket = new ServerSocket(PORT);
            while(true){
                socket = serverSocket.accept();

                BufferedReader br = new BufferedReader(
                        new InputStreamReader(socket.getInputStream()));
                ArrayList<String> cmd = new ArrayList<>();
                String in;
                while( (in = br.readLine()) != null ){
                    cmd.add(in);
                }
                command(cmd);
                if( socket != null){
                    socket.close();
                }
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

        if( serverSocket != null){
            try {
                serverSocket.close();
                serverSocket = null;
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    // send message to client
    private void sendMessage(String str) {
        System.out.println(str);
        try {
            OutputStream output = socket.getOutputStream();
            BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(output));
            bw.write(str + "¥n");
            bw.flush();
            bw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // error
    private void printError(String err) {
        String str = "ERROR; ";
        str += err;
        sendMessage(str);
    }

    public void command(ArrayList<String> cmd) {
        String mode = cmd.get(0);
        if(mode == null){

        }else switch(mode){
            case "MANUAL_SIG-ALL":
                System.out.println("全照明一括 信号値指定調光");
                manualSigAll(cmd.get(1));
                break;
            case "MANUAL_SIG-INDIVIDUAL":
                System.out.println("全照明独立 信号値指定調光");
                manualSigIndividual(cmd.get(1));
                break;
            case "MANUAL_ID-SIG":
                System.out.println("照明ID・信号値指定調光");
                manualIDSig(cmd.get(1));
                break;
            case "MANUAL_ID-RELATIVE":
                System.out.println("照明ID・相対信号値指定調光");
                break;
            case "DOWNLIGHT_ALL":
                System.out.println("Downlight: All Control");
                downlightAll(cmd.get(1));
                break;
            case "DOWNLIGHT_INDIVIDUAL":
                System.out.println("Downlight: Individual control");
                downlightIndividual(cmd.get(1));
                break;
            case "GET_LIGHTS":
                System.out.println("Sending lights via JSON");
                sendLights();
                break;
            default:
                System.out.println("Error: 不明なmode command");
        }
    }

    // 全照明一括 信号値指定調光
    private void manualSigAll(String sigs) {
        if(sigs == null) {
            System.out.println("信号値のフォーマットを確認してください");
        } else {
            ArrayList<Integer> s = new ArrayList<>();
            String[] buf = sigs.split(",");
            for(String i:buf) s.add(Integer.parseInt(i));
            for(Light l: ils.getLights()) {
                l.setLumPct((double)s.get(0)/255.0*100.0);
                l.setSignal(s.get(0), s.get(1));
            }
        }
        // 調光
        ils.downlightDimmer.send();

    }

    // 全照明独立 信号値指定調光
    private void manualSigIndividual(String sigs) {
        if(sigs == null) {
            System.out.println("信号値のフォーマットを確認してください");
        } else {
            ArrayList<Integer> s = new ArrayList<>();
            String[] buf = sigs.split(",");
            for(String i:buf) s.add(Integer.parseInt(i));
            for(int i=0; i<ils.getLights().size(); i++) {
                ils.getLights().get(i).setSignal(s.get(0), s.get(1));
                s.remove(0);
                s.remove(0);
            }
        }
        ils.downlightDimmer.send();
    }

    // 照明ID・信号値指定調光
    private void manualIDSig(String sigs) {
        if(sigs == null) {
            System.out.println("信号値のフォーマットを確認してください");
        } else {
            ArrayList<Integer> s = new ArrayList<>();
            String[] buf = sigs.split(",");
            for(String i:buf) s.add(Integer.parseInt(i));
            System.out.println(s.get(0));
            ils.getLight(s.get(0)).setSignal(s.get(1), s.get(2));
        }
        ils.downlightDimmer.send();
    }

    private void downlightAll(String cmd) {
        if(cmd == null) {
            printError("Check for data command.");
        } else {
            ArrayList<Double> data = new ArrayList<>();
            String[] buf = cmd.split(",");
            for(String i:buf) data.add(Double.parseDouble(i));
            for(Light l: ils.getLights()) {
                l.setLumPct(data.get(0));
                l.setTemperature(data.get(1));
            }
        }
        // dimming
        ils.downlightDimmer.send();
    }

    private void downlightIndividual(String cmd) {
        if(cmd == null) {
            printError("Check for data command.");
        } else {
            ArrayList<Integer> id = new ArrayList<>();
            ArrayList<Double> lumPct = new ArrayList<>();
            ArrayList<Integer> temp = new ArrayList<>();

            String[] buf = cmd.split(",");
            if(buf.length % 3 != 0) {printError("invalid number of data.");}

            for(int i=0; i<buf.length/3; i++) {
                int n = i*3;
                try {
                    id.add(Integer.parseInt(buf[n]));
                    lumPct.add(Double.parseDouble(buf[n + 1]));
                    temp.add(Integer.parseInt(buf[n + 2]));
                } catch (Exception e) {
                    printError(e.getMessage());
                    return;
                }
            }

            while (id.size() > 0) {
                // update light object
                Light light = ils.getLight(id.get(0));
                light.setLumPct(lumPct.get(0));
                light.setTemperature(temp.get(0));

                // remove data from array list
                id.remove(0);
                lumPct.remove(0);
                temp.remove(0);
            }

            // dimming
            ils.downlightDimmer.send();

        }
    }

    private void sendLights() {
        ObjectMapper mapper = new ObjectMapper();
        String json = "";
        try {
            json = mapper.writeValueAsString(ils.getLights());
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }

        // output
        sendMessage(json);
    }



}

Answer 1

如果您的服务器正在使用 readLine()，这很可能会阻塞，直到您关闭连接，因为您没有发送一条线。 p>

在flush()之前添加bw.newLine()

编辑 正如预测的那样，您的服务器没有发送线路，因此它需要与上述相同的处理方式。但是有一个前面的问题:

while( (in = br.readLine()) != null ){
    cmd.add(in);
}

服务器中的这个循环不可能退出直到客户端关闭连接。您应该在服务器中一次处理一行，或者降低您对客户端行为的期望。