从轮询线程连接到远程端口（服务器）

Question

我想从线程连接到远程服务器并继续发送字符串。如果连接被拒绝，线程应该继续轮询端口，直到服务器再次启动。我该如何处理这个异常并保持我的线程不会崩溃？服务器可能很长时间没有启动，但线程应该无限期地运行。

public void SendMessage(String message){
    try {
        socket = new Socket(actuatorAddress, destPort.get());
        outToServer = socket.getOutputStream();
        out = new DataOutputStream(outToServer);
        out.flush();
        out.write(message.getBytes());
    } catch (IOException ex) {
        System.out.println(ex.getMessage());
    } catch (Exception e) {
        System.out.println(e.getMessage());
    }
}

我更改了部分代码，如下所示。第一次调用 Connect 函数，随后通过线程调用 Send Message 函数。添加到重新连接的延迟有助于减少由于连接到非现有服务器而重复出现的时间延迟。还是觉得基本问题可能有更好的解决方案。

public boolean ConnectToActuator() {
    try {
        if(actuatorAddress.isReachable(2000)){
            socket = new Socket();
            socket.setPerformancePreferences(1, 2, 0);
            socket.setTcpNoDelay(false);
            socket.setSendBufferSize(32);
            socket.connect(new InetSocketAddress(actuatorAddress, destPort.get()));
            outToServer = socket.getOutputStream();
            out = new DataOutputStream(outToServer);
            connected = true;
            disconnectedTimeout = 0;
        }
    }catch (ConnectException e) {
        // TODO Auto-generated catch block
        System.out.println(e.getMessage());
    }catch (IOException ex) {
        connected = false;
        System.out.println(ex.getMessage());
    }
    return connected;
}

public boolean SendToActuator(String message) {
    if(connected == false){ //socket.isOutputShutdown()
        disconnectedTimeout++;
        if(disconnectedTimeout>20){
            disconnectedTimeout = 0;
            ConnectToActuator();
        } else {
            return connected;
        }
    }
    try {
        out.flush();
        out.writeBytes(message);
        disconnectedTimeout = 0;
        connected = true;
    } catch (UnknownHostException uhe) {
        connected = false;
        System.out.println(uhe.getMessage());
    } catch (IOException ioe) {
        connected = false;
        System.out.println(ioe.getMessage());
    }
    return connected;
}

Answer 1

鉴于 cmets 中的以下约束：

• 尝试将消息发送到 10 个服务器之一。
• 如果没有服务器可用于接收消息，则丢弃该消息。

你真正想做的是：

1. 遍历服务器地址列表
2. 尝试向每个人发送消息
3. 成功后立即跳出循环
4. 捕获连接失败的任何错误并尝试下一个服务器

这是一个将贯穿该场景的示例类。

import java.io.DataOutputStream;
import java.io.OutputStream;
import java.net.Socket;

public class MessageSender {
  private static final Integer destPort = 1234;

  private static final String[] serverAddresses = {
    "address1",
    "address2",
    "address3" // Etc....
  };

  public Boolean SendMessage(String message) {
    Boolean messageSentSuccessfully = false;
    for (String addy : serverAddresses) {
      messageSentSuccessfully = SendMessageToServer(addy, message);
      if (messageSentSuccessfully) {
        break;
      }
    }
    return messageSentSuccessfully;
  }

  private Boolean SendMessageToServer(String serverAddress, String message) {
    Boolean messageSent = false;
    try {
      Socket dataSocket = new Socket(serverAddress, destPort);
      OutputStream outToServer = dataSocket.getOutputStream();
      DataOutputStream out = new DataOutputStream(outToServer);
      out.write(message.getBytes());
      out.flush();
      messageSent = true;
    } catch (Exception e) {
      System.out.println(e);
    }
    return messageSent;
  }
}

希望对您有所帮助。

Answer 2

伪：

while(true){
  if(connect()) DoClientConnectedStuff();
  sleep(reconnectTimeout);
};

Answer 3

请尝试以下更改。如果您的连接拒绝，它将等待 2 秒（2000 毫秒），然后再次尝试连接服务器。如果连接成功，它将获取输出流，在 while 循环中写入数据并刷新数据。

public void createSocketConnection() throws IOException
{     
    socket = new Socket(actuatorAddress, destPort.get());
    if(socket!=null)
        {
          outToServer = socket.getOutputStream();
          out = new DataOutputStream(outToServer);
        }

}

public void SendMessage(String message){
    boolean isRunning=false;
    try 
    {
        createSocketConnection();
        isRunning=true;
        while(isRunning)
        {
          out.write(message.getBytes());
          out.flush();
       }
    } catch (java.net.ConnectException conExcp) {
        System.out.println(ex.getMessage());
        try{
          Thread.sleep(2000);
        }catch(Exception ee){}
    } 
    catch (IOException ex) {
        System.out.println(ex.getMessage());

    } 
}