code: public void setPortOffset(String socketBindingGroupName, String sysPropName, int offset) throws Exception {
          String offsetValue;
          if (sysPropName != null) {
              offsetValue = "${" + sysPropName + ":" + offset + "}";
          } else {
              offsetValue = String.valueOf(offset);
          }
  
          Address addr = Address.root().add(SOCKET_BINDING_GROUP, socketBindingGroupName);
          ModelNode request = createWriteAttributeRequest(PORT_OFFSET, offsetValue, addr);
          ModelNode results = execute(request);
          if (!isSuccess(results)) {
              throw new FailureException(results);
          }
          return; // everything is OK
      }
docs: Sets the port offset for the socket bindings found in the named socket binding group.
  If sysPropName is null, this simply sets the offset explicitly to the given offset.
  If sysPropName is not null, this sets the offset to the expression "${sysPropName:offset}".
  You typically will want to use the standard {@link #JBOSS_SYSPROP_PORT_OFFSET} system property
  name as the sysPropName to follow the normal out-of-box JBossAS configuration, though you don't have to.
  
  @param socketBindingGroupName name of the socket binding group whose port offset is to be set
  @param sysPropName the name of the system property whose value is to be the port offset
  @param offset the default port offset if the sysPropName is not defined
  @throws Exception any error