java : spawning new thread is causing original thread to halt
I have the following code in which I spawn a thread listen which is supposed to constantly listen to any incoming TCP messages, after this thread is run I want the main thread to be used for sending messages but as soon as I initiate listen.run() it seems that main thread does not run any further. I want it to continue to run the while loop but it never reaches it.
package tcpclient;
import java.io.*;
import java.net.*;
import java.net.UnknownHostException;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;
public class client {
//instance vars
static Socket cSocket =null;
static PrintWriter out = null;
static BufferedReader in = null;
//server info
static String serverName = null;
static int serverPort = 0;
static String userName=null;
//listening vars
static Thread listen;
static String incoming=null;
/**
* @param args the command line arguments
*/
public static void main(String[] args) throws IOException {
try {
System.out.println("\n\n\nTCP Chat Client\n\nEnter server name:");
Scanner scan = new Scanner(System.in);
//get server info from user
serverName = scan.nextLine();
System.out.println("\nEnter port number:");
serverPort = 开发者_如何学运维Integer.parseInt(scan.nextLine());
System.out.println("\nEnter your username:");
userName = scan.nextLine();
//make connection to server
cSocket = new Socket(serverName, serverPort);
out = new PrintWriter(cSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(cSocket.getInputStream()));
//send username to server
out.println(userName);
//start listening
listen = new Thread(){
@Override
public void run(){
try {
incoming = in.readLine();
while (!(incoming.equals(null))) {
System.out.print(incoming);
incoming = in.readLine();
}
} catch (IOException ex) {
Logger.getLogger(client.class.getName()).log(Level.SEVERE, null, ex);
}
}
};
listen.run();
String rcvrname="wefwef";
String message=null;
//start messaging
while(!(rcvrname.equals("exit"))){
System.out.println("Enter reciever name");
out.println(scan.nextLine());
System.out.println("Enter message");
out.println(scan.nextLine());
}
out.close();
in.close();
cSocket.close();
}
catch (UnknownHostException ex) {
System.err.println("\ncan't find that host\n");
}
catch (IOException ex) {
Logger.getLogger(client.class.getName()).log(Level.SEVERE, null, ex);
}
finally{
in.close();
out.close();
cSocket.close();
}
}
}
You want:
listen.start();
not
listen.run();
Also the preferred way of doing this since Java 5 is to use an ExecutorService
:
Runnable listen = new Runnable() {
public void run() { ... }
}
ExecutorService exec = Executors.newSingleThreadExecutor();
exec.submit(listen);
and when you want to stop it:
exec.shutdown();
exec.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
or simply:
exec.shutdownNow();
Here is the problem:
listen.run();
You mustn't call run()
itself! You should call start()
, this spawns a thread, calling run()
just call a function.
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