Writing messages to client socket using DataOutputStream to Server Socket only sent after closing the Client Socket why?

问题

I had a Socket-Client programming in Java . I am using DataOutputStream to send messages to the Server Socket . Sometimes writed messages on DataOutputstream was not sent to the ServerSocket . I think it's due to i am not flushing after sent message . I do this but no use . If I terminate the class execution then only I receive messages from ServerSocket .

My CODE :

public class LoggingClient {


LinkedBlockingQueue<byte[]> messages = new LinkedBlockingQueue<byte[]>();

public static LoggingClient clientObj;

/*
 * waiting 2 seconds for connecting centralized log server . If it's not reachable writing log's in local machine
 * this log's will be collected on eclipse restart.
 */
public static final int SOCKET_TIMEOUT = 2000;
/**
 * Server which the log server is currently running.
 */
public static final  String SERVER = "bharathi";
/**
 * Port which the log server is running.
 */
public static final int PORT = 10000;

/**
 * Client socket used to connect the server .
 */
Socket client = null;

public static Logger logger = Logger.getLogger(LoggingClient.class.getName());


/**
 * Used to write given logs into client output stream.
 */
DataOutputStream out = null;

public boolean isConnected = false;

/**
 * Used for preventing instaniate LoggingClient without calling getInstance method.
 */
private LoggingClient(){

}

/**
 * Clear's the socket and initialize new socket .
 */
public void init(){
try{
    clear();
    client = new Socket();
        client.setTcpNoDelay(true);
    client.connect(new InetSocketAddress(SERVER,PORT),SOCKET_TIMEOUT); //trying to make connection within two seconds.
    out = new DataOutputStream(client.getOutputStream());
    isConnected = true;
}catch(Exception e){
    isConnected = false;
}
}

public static LoggingClient getInstance(){
if(clientObj == null){
    clientObj = new LoggingClient();
}
return clientObj;
}

public void clear(){
try{
    if(out != null){
    out.close(); //if we call close method it invokes flush and then closes the DataOutputStream.
    }

    if(client != null){
    client.close();
    }
}catch(Exception e){
    logger.log(Level.INFO,"Error while closing connection , reason {0}",e);
}finally{
    try{
    client.close();
    out.close();
    }catch(Exception e){

    }
    isConnected = false;
}
}


/**
 * Adding this message into a queue . Scheduled thread will get this logs and push into central logging server.
 * @param message
 */
public synchronized void write(byte[] message){
if(!isConnected){ //has connection.
    init();
}
messages.add(message); //adding message to this queue . Background thread will collect the log message and sent it to the central log server.
}

/**
 * Sending logs into central log server . If it's not reachable write into local machine.
 * @param message
 */
public void sendLog(byte[] message){
try {
    out.write(message);
    out.flush();
} catch (Exception e) {
    writeInLocalMachine(localLoggingPath, message); //in case of failure writing logs in local machine . Sync this logs when restart of eclipse.
}
}

/**
 * Writing log's into his machine this log will be synced on plugin startup.
 * @param file - File path.
 * @param message - Message  to log.
 */
public static void writeInLocalMachine(String file, byte[] message) {
FileOutputStream fileWriter = null;
File f = new File(file);
try {
    if(!f.exists()){
    f.createNewFile();
    }
    fileWriter = new FileOutputStream(file, true);
    fileWriter.write(message);
    fileWriter.flush();
} catch (Exception e) {
   logger.log(
        Level.WARNING,
        "This may be due to given file not found in system , reason {0}",
        e);
} finally {
    try{
    fileWriter.close();
    }catch(Exception e){

    }
}
}

/**
 * @return - Recently received message from queue . Returns null if it's empty.
 */
public byte[] getMessage(){
return messages.poll(); //returns the head element and deletes it.
}

}

Testing java class for sending messages to server socket .

public class LogTest implements Runnable {

public static final String LINE_SEPARATOR = System.getProperty("line.separator");


@Override
public void run() {
while(true){
    try{
        LoggingClient client = LoggingClient.getInstance();
        byte[] message = client.getMessage();
        if(message != null){
            client.sendLog(message);
        }
    }catch(Exception e){

    }
}
}

public static void startSending(){
for(int i=0;i<10000;i++){
    String msg = "msg number" + i+LINE_SEPARATOR;
    LoggingClient.getInstance().write(msg.getBytes());
}
}

public static void main(String args[]){
    LoggingClient c = LoggingClient.getInstance();
    System.out.println("START TIME " + System.currentTimeMillis());
    Thread t = new Thread(new LogTest(),"LOG MESSAGER");
    t.start();
    startSending();
    System.out.println("END TIME " + System.currentTimeMillis());
}

Sent messages will be stored in a file .

Ouput :

START TIME 1340815857896
END TIME 1340815858063

Finished putting messages into the queue . The infinite while loop will take care of sending logs into the server socket .

Content Stored In file is 0 bytes why ? . If i stop running class I receive sent messages why?

回答1:

You have posted too much code, but 99 times out of 100 in these cases where you only see the data after the stream / program has closed your problem is that you are never flushing the data after it is written

回答2:

Have you tried calling SetSockOption with TCP_NODELAY?

http://docs.oracle.com/javase/6/docs/api/java/net/SocketOptions.html
http://www.ibm.com/developerworks/linux/library/l-hisock/index.html
http://en.wikipedia.org/wiki/Nagle%27s_algorithm

来源：https://stackoverflow.com/questions/11231365/writing-messages-to-client-socket-using-dataoutputstream-to-server-socket-only-s

标签

java

sockets

java-ee

serversocket