When china stopped trading with most of the world only the city of was open to trade?

With Hong Kong being part of the British Empire until 1997, Canton (now known as Guangzhou) was the only city opened by the Chinese to trade with the West. Trade was conducted during the bi-annual Canton Trade Fair, where western and Asian traders met with their Chinese counterparts in order to trade metals,minerals, raw materials, and whatever other goods mainland China needed to buy or sell.