J2ME的HTTP连接，服务器出现EOFException

问题是这样的，J2ME的HTTP连接，服务器出现EOFException,模拟器上联服务器 一点问题都没有， 可是换上真机后
程序启动：第一次联，无错
不关闭程序 第二次联，首先出现 EOFException，问题好像出在readUTF()上，但是马上会有第二次连接，返回结果到客户端
不关闭程序，同时把发送出去的字符串加长，则出现EOFException，而且不会再有连接出现，程序就死那里了

客户端联网部分如下

private void connect(String url) throws IOException {

HttpConnection httpConn = null;

DataOutputStream dos = null;

DataInputStream dis = null;

String s = null;
String s1 = null;
try {

System.out.println("connection to server...");
//httpConn = (HttpConnection)Connector.open(url);


//如果用模拟器，将此处向下注释，上行取消注释
 
httpConn = (HttpConnection)Connector.open("http://10.0.0.172/"+url);
httpConn.setRequestProperty("X-Online-Host","sina.cn");

s1 = httpConn.getHeaderField("Content-Type");  
//资费页
if(s1.startsWith("text")){

//重新发起一次请求
httpConn = (HttpConnection)Connector.open("http://10.0.0.172/"+url);
httpConn.setRequestProperty("X-Online-Host", "sina.cn");
//s1 = "send again";
}
// 
//用模拟器注释到此
System.out.println("OK");


// 传送数据

httpConn.setRequestMethod(HttpConnection.POST);
System.out.println("good");

dos = new DataOutputStream(httpConn.openDataOutputStream());
System.out.println("write");
dos.writeUTF(userName);
  dos.writeUTF(password);
System.out.println("write");

//dos.flush();
// 接收servlet判断的数据

dis = new DataInputStream(httpConn.openDataInputStream());

String returnStr = dis.readUTF();


//int returnStr = dis.readInt();
//s = new String("returnStr:" + returnStr + " " + httpConn.getLength() + " " + httpConn.getURL().getBytes().length);
s = new String("returnStr:" + returnStr);
} catch (IOException e) {

e.printStackTrace();

} finally {
if (dis != null)
dis.close();
if (dos != null)
dos.close();
if (httpConn != null)
httpConn.close();
}

// 显示返回的结果

midlet.endMIDlet(s);

}


服务器端如下：

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

this.doGet(request, response);
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

String username = "";
String password = "";

System.out.println("Connecting Server.....");

DataInputStream dis = null;
dis = new DataInputStream(request.getInputStream());

try{
username = dis.readUTF();
password = dis.readUTF();

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

}
finally{
if (dis != null){
dis.close(); 
dis = null;
}
}

DataOutputStream dos = new DataOutputStream(response.getOutputStream());
try{
String returnStatus = "-1";
System.out.println(returnStatus);
dos.writeUTF(returnStatus);
}catch(Exception e) {
e.printStackTrace();
}
finally{
if (dos != null){
dos.close();
dos = null;
}
}
}


请大虾们赐教，谢谢


------解决方法--------------------------------------------------------
要确定下具体出错的代码位置才好分析
------解决方法--------------------------------------------------------
自己先确定一下究竟是否是移动资费页面的问题，有时候返回了移动资费页面而你去readUTF的话就会出现你这样的问题．