A problem of JavaCOG

I submit an execution task. The COG program seems to wait forever. But the task actually is executed by the remote server.
The reason seems to be that: COG program expects response from remote server (Globus server or others), but the remote server does not return any response even if the task is completed successfully.
I don't know whether my understanding is correct. I tried different ways to submit a task.
(1) by using command line tool
    task 1: transfer a local file to remote machine using gridftp.
    cog-file-transfer.bat -s file:///E:/my_program/web_app/CogTest/bin/testkarajan.xml -d gsiftp://gf1.ucs.indiana.edu/home/zhguo/testkarajan.xml
    This can be completed successfully.
    task 2: execute a command on remote machine
    cog-job-submit.bat -s gf1.ucs.indiana.edu -e /bin/ls -stdout list.txt -d /home/zhguo -provider gt2
    This command hangs up forever and does not return control to user until it is terminated forcibly. But the corresponding command ( in this case, it is /bin/ls ") can be executed on remote machine and the result is written into the specified file.
    cog-job-submit.bat -s gf1.ucs.indiana.edu -e /bin/ls -stdout list.txt -d /home/zhguo -provider gt2 -b
    This works well.
    So, what is difference between batch mode and regular mode?
(2) by using GUI tool
     The same results as above.
(3) by using API
    I wrote a program which utilized the karajan engine to handle the karajan workflow related stuff.
    All kinds of invocation do not work well.

How to solve it? Is there anything I missed ?