Android Socket客户端循环

Question

Hello i have a problem with my android client loop , i tested the server with wireshark and i can see it sends the string just fine , when i debug the client i can see it runs good once but when it loops again and it retrieves the second string it looks like the Bufferedinput is empty and it never contione thought the .readline()

Android client :

 package com.example.leopard;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.Charset;

import android.R.string;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.os.IBinder;
import android.os.Vibrator;
import android.util.Log;
import android.widget.Toast;

public class leopardService extends Service{
    private boolean isRunning = false;
    private static final  String SERVER_IP = "192.168.178.11";
    private static final int SERVERPORT = 6000;
    private Socket socket;
    Thread ClientThread = null;
    String st = null;
    private Camera camera;


    public void onCreate() {

    }


    public int onStartCommand(Intent intent, int flags, int startId){
        super.onStartCommand(intent, flags, startId);

        // Annoucment about starting serivce

        // Start a Thread Called MyThread
        isRunning = true;
        this.ClientThread = new Thread(new ClientThread());
        this.ClientThread.start();

        // Keep running until it explicitly stopped.
        // stopped so returns sicky
        return START_STICKY;
    }
    // code


    public void onDestroy(){
        super.onDestroy();
        // stop background Thread
        isRunning = false;


    }

    public class ClientThread implements Runnable {
        public void run() {
            isRunning = true;

            {
                while( isRunning = true){
            try{
                InetAddress serverAddr = InetAddress.getByName(SERVER_IP);

                socket = new Socket(serverAddr,SERVERPORT);


                BufferedReader input =  new BufferedReader(new InputStreamReader(socket.getInputStream()));


                String st = input.readLine();

                if (st.equals("vibrate")){
                    Vibrator v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
                    v.vibrate(1000);
                }
                else if(st.equals("quit")){
                    Vibrator b = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
                            b.vibrate(3000);

                isRunning = false;
                }









            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    } 
        }




    }

    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;
    }

}

C server code incase needed:

#include <winsock2.h>
#include <stdio.h>

#define BUF_LEN 100

int main(int argc, char *argv[])
{
    WSADATA wsa;
    SOCKET s , new_socket;
    struct sockaddr_in server , client;
    int c;
    int result;
    char message[BUF_LEN];
    bool IsRunning;
    IsRunning = true;

if (WSAStartup(MAKEWORD(2,2),&wsa) != 0)
{
    printf("ERROR initlizaing winsock2 dll : %d",WSAGetLastError());
    return 1; // exit program with error.
}

printf("INitialised.\n");

// create a socket
 s = socket(AF_INET,SOCK_STREAM, 0);
if(s == INVALID_SOCKET)
{
    printf("error at creating socket :%d" ,WSAGetLastError());
    WSACleanup();
    return 1;
}

printf("socket created");

//Sockad_addr in strucsture prepare
memset(&server, 0, sizeof server);
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons(6000);

// bind the socket

if (bind(s , (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)
{
    printf("Bind fialed with errror code : %d",WSAGetLastError());
    closesocket(s);
    WSACleanup();
    return 1;
}


listen(s , 3);

printf("waiting for incoming connections");
// this part is what i dont understand.
c = sizeof(struct sockaddr_in);
new_socket = accept(s , (struct sockaddr *)&client,&c);
if(new_socket == INVALID_SOCKET)
{
    printf("accept fialed with error code : %d" ,WSAGetLastError());

    closesocket(s);
    WSACleanup();
    return 1;
}

printf("Connection acceptëd");
//message ="quit\n";
//reply to CLIENTCREATESTRUCT
while(IsRunning == true){
scanf("%s",message);
if(message == "stop_thread"){
    IsRunning = false;
}

strcat(message, "\n");
    result = send(new_socket , message , strlen(message) , 0);
    if(result == SOCKET_ERROR)
    {
        printf("send failed with error codfe %d\n",WSAGetLastError());

    }
    else{
        printf("sent %d bytes out of %u \n",result,strlen(message));
    }
memset(message, 0 ,100);
}
getchar();
closesocket(s);
WSACleanup();
return 0;
}

Answer 1

Your client creates new connections that read just 1 line (and then doesn't clean up / close the socket)

while( isRunning = true){
                socket = new Socket(serverAddr,SERVERPORT);
                string = readLine();
}

Your server on the other hand accepts 1 connection, reads within a loop from that connection and quits.

while(IsRunning == true){
    scanf("%s",message);
}
return 0;

Your server will not accept the second connection attempt and if it notices that the socket is eventually closed (which may not happen at all) it would just quit. So you should fix 2 things:

• Your server should have an additional loop to accept new connections once the first is closed. You could also consider creating a thread per accepted connection so it can handle more than just 1 client at a time.

• Your client should not open a new connection within the loop. You could add a loop to re-connect in case the connection drops though. And you must make sure that you close the connection properly so your server will eventually return from the loop.

Roughly this on client side

try{
    InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
    socket = new Socket(serverAddr,SERVERPORT);
    while( isRunning = true){
        .. readline
    }
} finally {
    if (socket != null) {
        // send "stop_thread", close OutputStream
        // close socket
    }
}