求大神解答 新手遇到的有关socket传输一个类时遇到的有关问题

求大神解答 新手遇到的有关socket传输一个类时遇到的问题
这是Server端代码

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.io.OutputStream;

import java.io.OutputStreamWriter;

import java.io.Serializable;

import java.net.ServerSocket;

import java.net.Socket;


import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;



public class ser_test{

		public static void main(String []args)	throws Exception

		{


			ServerSocket socketConnection =new ServerSocket(30000);

			System.out.println("start");

			Socket socket=socketConnection.accept();

			System.out.println("建立连接");


			ObjectInputStream in=new ObjectInputStream(socket.getInputStream());



			USER user=(USER) in.readObject();


			System.out.println("username"+user.getusername());

			System.out.println("password"+user.getpassword());



			OutputStream os=socket.getOutputStream();

			os.write("success".getBytes("utf-8"));


			os.close();

			socketConnection.close();


		}


}

这是client端代码

package com.related.firstactivity;


import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.DataOutputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.io.OutputStream;

import java.io.OutputStreamWriter;

import java.io.Serializable;

import java.net.Socket;

import java.net.UnknownHostException;





import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.Toast;


public class Lg_activity2 extends Activity{


	private Button login_bt;

	private Button register_bt;

	private EditText input_username;

	private EditText input_password;



	public void onCreate(Bundle savedInstanceState) {  

        super.onCreate(savedInstanceState); 

        setContentView(R.layout.login_regest);

        

        login_bt=(Button)findViewById(R.id.loginbt);

        register_bt=(Button)findViewById(R.id.register_bt);

        input_password=(EditText) findViewById(R.id.password);

        input_username=(EditText) findViewById(R.id.username);

        

        login_bt.setOnClickListener(new OnClickListener() {


			@Override

			public void onClick(View v) {

				// TODO Auto-generated method stub

				Thread loginThread = new Thread(new LoginThread());


				loginThread.start();

			}

		});

        

        register_bt.setOnClickListener(new OnClickListener() {


			@Override

			public void onClick(View v) {

				// TODO Auto-generated method stub

				Intent intent =new Intent();

				intent.setClass(Lg_activity2.this, Register.class);

				startActivity(intent);

			}

		});

	}



Handler handler= new Handler()

{

	 public void handleMessage(Message msg)

	 {

		 switch(msg.what)

		 {

		 case 0:

			 Toast.makeText(getApplicationContext(), "success", 0).show();

			 Intent intent=new Intent(Lg_activity2.this,MainActivity.class);

			 startActivity(intent);

			 finish();

			 break;

		 case 1:

			 Toast.makeText(getApplicationContext(), "faliure", 0).show();

			 break;

		 }

	 }

};

String loginServer(String username,String password)

{

	String reponseMsg="faliuer";

	try {

		Socket socket=new Socket("192.168.191.2",30000);



		ObjectOutputStream out=new ObjectOutputStream(socket.getOutputStream());


		USER user=new USER(username,password);


		out.writeObject(user);


		out.flush();



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

		reponseMsg=br.readLine();



	} catch (UnknownHostException e) {

		// TODO Auto-generated catch block

		e.printStackTrace();

	} catch (IOException e) {