Local port number. In the case of a passive entity, this is a public port number with respect to the client.
In the case of an active entity, this is normally specified as 0. When 0 is specified, an open port will automatically be selected. When something other than 0 is specified, it cannot connect unless that particular port number is open. In Windows, even if connection is broken, for a short while (several minutes) that port number is still appropriated. Please note that for this reason, if something other than 0 is specified, connection will not be possible for several minutes.
void SetLocalPortNumber(long lNewValue);