Restful server error in tomcat

Could anyone help a problem with the REST server?

I'm developing an android app and I'm working with a restful server, Postgres and Tomcat .

And I'm having this error almost every time I make several requests:

GRAVE: 
Servlet.service() for servlet [Jersey REST Service] in context with path [/Servidor] threw exception 
[javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Um erro de E/S
ocorreu ao enviar para o processo do servidor.] 
with root cause
java.net.SocketTimeoutException: Read timed out
  at java.net.SocketInputStream.socketRead0(Native Method)

And this error too:

[javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Um erro de E/S
ocorreu ao enviar para o processo do servidor.] 
with root cause
java.net.SocketTimeoutException: Read timed out
  at java.net.SocketInputStream.socketRead0(Native Method)