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?
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
Have you tried calling SetSockOption with TCP_NODELAY?
来源：https://stackoverflow.com/questions/11231365/writing-messages-to-client-socket-using-dataoutputstream-to-server-socket-only-s