Watford.
The match is to be played on Tuesday, July 16.
The Hornets signed midfielder Gavin Mahon from The Bees earlier this season and are linked with a move for defender Ivar Ingirmarsson, while former Griffin Park boss Ray Lewington now manages Watford's reserves.
The game will be played at Griffin Park, with a 7.45pm kick-off.
The match is to be played on Tuesday, July 16.
The Hornets signed midfielder Gavin Mahon from The Bees earlier this season and are linked with a move for defender Ivar Ingirmarsson, while former Griffin Park boss Ray Lewington now manages Watford's reserves.
The game will be played at Griffin Park, with a 7.45pm kick-off.