Java.lang.Exception: IOException in sending Request

The reason of this problem:
this problem will appear if you just change the Time Zone of your system.

Solution of the problem
To solve this problem you need to run "emctl resetTZ agent" like this:

1- Open the command prompt and type
set oracle_sid=(your DB name)
On unix bash shell
$export ORACLE_SID=DB_NAME
2- Then Type this command
$emctl resetTZ agent

3- You will see this message that will tell you what to do :

Oracle Enterprise Manager 10g Database Control Release 10.2.0.1.0
Copyright © 1996, 2005 Oracle Corporation. All rights reserved.
Updating D:\oracle\product\10.2.0\db_1/osama-pc_orcl/sysman/config/emd.properties...
Time zone set to Africa/Cairo.
To complete this process, you must either:
connect to the database served by this DBConsole as user 'sysman', and execute:
SQL>conn sysman/password
SQL> exec mgmt_target.set_agent_tzrgn('hostname','Africa/Cairo')
-- or --
connect to the database served by this DBConsole as user 'sys', and execute:
SQL> alter session set current_schema = SYSMAN;
SQL> exec mgmt_target.set_agent_tzrgn('hostname','Africa/Cairo');

Note that you have to use your machine hostname instead of hostname here.
Instead of Africa/Cairo enter your time zone.
4- You must restart the DBCONSOLE Service Or reboot your machine and you will find that the problem has gone.

$emctl stop dbconsole
$emctl start dbconsole