Http连接出错,该如何处理

Http连接出错
在执行到下面时出错，e.getmessage()=null:
Log.i("HttpGet","Get input stream");
InputStreamReader in = new InputStreamReader(conn.getInputStream());
Post方法是在:conn.connect();时出错，也是一样的异常信息。在模拟器中用浏览器打开网址是正常的。

package com.example.httptest;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.net.URI;
import java.net.URL;

import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.conn.ClientConnectionManager;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.HttpParams;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.EntityUtils;

import android.net.*;
import android.util.Log;

public class MyNetwork {
	//HTTP Get Method
	public static String HttpGet(String strServerName,String strURI,int port)
	{
		String strResult = "";
		int iPort = port;
		
		//合并URL字符串
		String strURL = String.format("http://%1$s:%2$d%3$s", strServerName,iPort,strURI);
		Log.i("HttpGet","URL:"+strURL);
		
		URL url = null;
		try
		{
			url = new URL(strURL);
			//创建HTTP连接
			Log.i("HttpGet","Connection to Server...");
			HttpURLConnection conn = (HttpURLConnection)url.openConnection();			
			Log.i("HttpGet","Connected");
			//获取输入流字符串
			Log.i("HttpGet","Get input stream");
			InputStreamReader in = new InputStreamReader(conn.getInputStream());
			//转换为buffstream
			Log.i("HttpGet","Convert to BufferedReader");
			BufferedReader bufferread = new BufferedReader(in);
			//将接收到的数据转为字符串
			String strtemp = null;
			Log.i("HttpGet","Bufferread readline");
			while((strtemp=bufferread.readLine()) != null)
			{
				strResult += strtemp;
			}
			Log.i("HttpGet",strResult);
			Log.i("HttpGet","input stream close");
			//关闭字符串流
			in.close();
			//关闭连接
			Log.i("HttpGet","Disconnect");
			conn.disconnect();
		}
		catch(SocketException e)
		{
			Log.i("HttpGet","SocketException:"+e.getMessage());
			strResult = String.format("Error:%1$s", e.getMessage());
		}
		catch(SocketTimeoutException e)
		{
			Log.i("HttpGet","SocketTimeoutException:"+e.getMessage());
			strResult = String.format("Error:%1$s", e.getMessage());
		}
		catch(FileNotFoundException e)
		{
			Log.i("HttpGet","FileNotFoundException:"+e.getMessage());
			strResult = String.format("Error:%1$s", e.getMessage());
		}
		catch(IOException e)
		{
			Log.i("HttpGet","IOException:"+e.getMessage());
			strResult = String.format("Error:%1$s", e.getMessage());
		}
		catch(Exception e)
		{
			e.printStackTrace();
			Log.i("HttpGet","Error:"+e.getMessage());
			strResult = String.format("Error:%1$s", e.getMessage());
		}
		
		return strResult;
	}
	
	//HTTP Post Method
		public static String HttpPost(String strServerName,String strURI,String strParams,int port)
		{
			String strResult = "";
			int iPort = port;
			
			//合并URL字符串
			String strURL = String.format("http://%1$s:%2$d%3$s", strServerName,iPort,strURI);
			Log.i("HttpPost","URL:"+strURL);
			
			URL url = null;
			try
			{
				url = new URL(strURL);
				//创建HTTP连接
				Log.i("HttpPost","Connection to Server...");
				HttpURLConnection conn = (HttpURLConnection)url.openConnection();
				conn.setDoInput(true);//设置输入流采用字节流
				conn.setDoOutput(true);//设置输出流采用字节流
				conn.setRequestMethod("POST");
				conn.setUseCaches(false);//不使用缓存
				conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");//设置参数
				conn.setRequestProperty("Charset", "utf-8");
				conn.connect();//连接
				Log.i("HttpPost","Connected");
				//发送参数
				Log.i("HttpPost","send params");
				DataOutputStream dop = new DataOutputStream(conn.getOutputStream());
				dop.writeBytes(strParams);
				dop.flush();//发送，清空缓存
				dop.close();//关闭
				//获取输入流字符串
				Log.i("HttpPost","Get input stream");
				InputStreamReader in = new InputStreamReader(conn.getInputStream());
				//转换为buffstream
				Log.i("HttpPost","Convert to BufferedReader");
				BufferedReader bufferread = new BufferedReader(in);