【发布时间】：2016-11-12 01:22:57
【问题描述】：
下面的代码工作并在预定时间发送消息，但我认为每次计时器执行预定任务时打开新套接字不是一个好的解决方案。我想要的是只在运行方法中打开一次套接字，并在计时器中创建新的类实例时在 SendMessage 类中访问它。这样它不起作用，它只发送一条消息然后停止发送。此外，对于一些关于代码或使其线程安全的提示的批评者，我会很高兴。
public class Client implements Runnable{
// Client Constructor here
@Override
public void run(){
//SENDS ONLY ONE MESSAGE
pitcherSocket = new Socket(InetAddress.getByName(hostname), port);
Timer timer = new Timer();
timer.schedule(new SendMessage(), 0, 1000/mps);
}
private class SendMessage extends TimerTask{
private int id;
@Override
public void run() {
try
{ // THIS WORKS FINE, SENDS MESSAGES AT SCHEDULED TIME
pitcherSocket = new Socket(InetAddress.getByName(hostname), port);
OutputStream outToServer = pitcherSocket.getOutputStream();
DataOutputStream out = new DataOutputStream(outToServer);
out.writeInt(id);
out.flush();
}catch(IOException e)
{
e.printStackTrace();
}
}
}
}
编辑：完整代码
客户
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
public class Pitcher implements Runnable{
private int port;
private int mps;
private int size;
private String hostname;
private List<Integer> messageIds = Collections.synchronizedList(new ArrayList<Integer>());
private Socket pitcherSocket;
//constatns, integer is 4 bytes, long is 8 bytes
private static final int INT_SIZE = 4;
private static final int LONG_SIZE = 8;
public Pitcher(int port, int mps, int size, String hostname) {
this.port = port;
this.mps = mps;
this.size = size;
this.hostname = hostname;
}
@Override
public void run(){
System.out.println("Pitcher running...");
System.out.println();
Timer timer = new Timer();
timer.schedule(new SendMessage(), 0, 1000/mps);
timer.schedule(new DisplayStatistics(), 0, 1000/mps);
}
//Nested class that sends messages
private class SendMessage extends TimerTask{
private int numberOfSentMessages = 0;
private int id;
@Override
public void run() {
try {
pitcherSocket = new Socket(InetAddress.getByName(hostname), port);
OutputStream outToServer = pitcherSocket.getOutputStream();
DataOutputStream out = new DataOutputStream(outToServer);
//send message size
out.writeInt(size);
//message id is same as number of the sent message
id = numberOfSentMessages + 1;
out.writeInt(id);
messageIds.add(id);
//get system timestamp
long currentTimestamp = System.currentTimeMillis();
out.writeLong(currentTimestamp);
//fill in the rest-
byte[] rest = new byte[size - 2 * INT_SIZE - LONG_SIZE]; //message size(default 300 bytes) - size(4 bytes) - message id(4 bytse) - timestamp(8 bytes)
out.write(rest);
out.flush();
numberOfSentMessages++;
InputStream inFromServer = pitcherSocket.getInputStream();
DataInputStream in = new DataInputStream(inFromServer);
Integer catcherMessageSize = in.readInt();
Integer catcherId = in.readInt();
long catcherTimestamp = in.readLong();
System.out.println("Sent message: " + size + " " + id + " " + currentTimestamp + "...");
System.out.println("Received message: " + catcherMessageSize + " " + catcherId + " " + catcherTimestamp + "...");
System.out.println();
}catch(IOException e)
{
e.printStackTrace();
}
}
}
}
服务器
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 java.net.SocketTimeoutException;
public class Catcher implements Runnable{
private int port;
private String bind;
private ServerSocket serverSocket;
//constatns, integer is 4 bytes, long is 8 bytes
private static final int INT_SIZE = 4;
private static final int LONG_SIZE = 8;
public Catcher(int port, String bind) {
this.port = port;
this.bind = bind;
}
@Override
public void run() {
System.out.println("Catcher running...");
System.out.println();
try {
serverSocket = new ServerSocket(port, 100, InetAddress.getByName(bind));
}
catch (IOException e1) {
e1.printStackTrace();
}
while(true){
try
{
Socket server = serverSocket.accept();
DataInputStream in = new DataInputStream(server.getInputStream());
Integer pitcherMessageSize = in.readInt();
Integer pitcherId = in.readInt();
long pitcherTimestamp = in.readLong();
DataOutputStream out = new DataOutputStream(server.getOutputStream());
//message id and size are sent back
out.writeInt(pitcherMessageSize);
out.writeInt(pitcherId);
//send back current time
long currentTimestamp = System.currentTimeMillis();
out.writeLong(currentTimestamp);
//fill in the rest
byte[] rest = new byte[pitcherMessageSize - 2 * INT_SIZE - LONG_SIZE]; //message size(default 300 bytes) - size(4 bytes) - message id(4 bytes) - timestamp(8 bytes)
out.write(rest);
out.flush();
System.out.println("Received message: " + pitcherMessageSize + " " + pitcherId + " " + pitcherTimestamp + "...");
System.out.println("Sent message: " + pitcherMessageSize + " " + pitcherId + " " + currentTimestamp + "...");
System.out.println();
//server.close();
}
catch(SocketTimeoutException s){
System.out.println("Socket timed out!");
break;
}
catch(IOException e){
e.printStackTrace();
break;
}
}
}
}
【问题讨论】：
-
您是否看到任何异常？当它停止发送时，程序是结束还是只是挂起？
-
也不例外，服务器收到第一个id，继续监听。客户端计时器仍然执行 SendMessage 类并尝试发送，但在第一次迭代后没有发送任何内容
-
据我所知，您正在按计划创建和执行
SendMessage。SendMessage每次创建时都会尝试通过Socket重新连接。 -
你知道为什么它没有重新连接吗？
-
显示你的服务器端代码。您是否每次都终止连接并重新建立？还是你只在客户端做？您也永远不会关闭套接字客户端。我不确定您为什么要连接、发送消息、断开连接然后重新连接。我是不是误会了什么？
标签： java multithreading sockets