What groups did east african countries most often trade with?

The east african communities most often trade with the Arabs and the Asians

During the Indian ocean trade, long distance Bantu communities traded with Arabs from Oman,Yemen, and Persia as early as 1000ad, and earlier than that. there were already established city states around the east coast of Africa, with the Swahili, a half cast of the Bantus and Arabs, acting as middle men. The lucrativeness of the trade even forced an Oman sultan, Said  to transfer his capital from muscat to Zanzibar.