public static TcpConnectionManager getConnectionPool(EndPoint from, EndPoint to) {
   String key = from + ":" + to;
   TcpConnectionManager cp = poolTable_.get(key);
   if (cp == null) {
     lock_.lock();
     try {
       cp = poolTable_.get(key);
       if (cp == null) {
         cp =
             new TcpConnectionManager(
                 MessagingConfig.getConnectionPoolInitialSize(),
                 MessagingConfig.getConnectionPoolGrowthFactor(),
                 MessagingConfig.getConnectionPoolMaxSize(),
                 from,
                 to);
         poolTable_.put(key, cp);
       }
     } finally {
       lock_.unlock();
     }
   }
   return cp;
 }