* @param host name of host if direction is SG_IO_OUT or SG_IO_BI
* @param port port number if we care to choose one.
* @param style specify "udp" or "tcp" */
* @param host name of host if direction is SG_IO_OUT or SG_IO_BI
* @param port port number if we care to choose one.
* @param style specify "udp" or "tcp" */