It's hard to talk about a tighly knit literary community in present day Istanbul. Beyoglu and its Istiklal Street used to be the place but very little remains of such places where writers, artists gather. One of the few are Kaktus Cafe on Istiklal Street, Kitchenette under The Marmara Hotel in Taksim.
Also, conservative Turkish newspaper Zaman names the following as literary hangouts in one of the recently published articles. Corlu'lu Alipaşa Medresesi (Nargile and Tea Garden) in Beyazit, Koca Sinan Paşa Medresesi (Tea Garden) in Cemberlitas (after entering the gate to Koca Sinan Paşa’s tomb, go past the cemetery – it’s the second teahouse to the right). Eski Kafa in At Pazari in Fatih.