why to make many restful with the same client we get this error?
One answer
It sounds like connections are being refused, you may simply have not configured enough http threads in your servlet container, the default settings are quite low particularly for Tomcat.
Tuning guides are available:
If you are running with Websphere you may also want to read
Tuning IBM HTTP Server to maximize the number of client connections to WebSphere Application Server
Tuning IBM HTTP Server to maximize the number of client connections to WebSphere Application Server