Wikipedia
The Haijin or sea ban was a series of related isolationist Chinese policies restricting private maritime trading and coastal settlement during most of the Ming dynasty and some of the Qing. First imposed to deal with Japanese piracy amid the mopping up of Yuan partisans, the sea ban was completely counterproductive: by the 16th century, piracy and smuggling were endemic and mostly consisted of Chinese who had been dispossessed by the policy. China's foreign trade was limited to irregular and expensive tribute missions, and resistance even to them among the Chinese bureaucracy led to the scrapping of Zheng He's fleets. Piracy dropped to negligible levels only upon the end of the policy in 1567, but a modified form was subsequently adopted by the Qing. This produced the Canton system of the Thirteen Factories, but also the opium smuggling that led to disastrous wars with Britain and other European powers in the 19th century.
The policy was also mimicked by both Tokugawa Japan (as the Sakoku) and Joseon Korea, which became known as the " Hermit Kingdom", before they were opened militarily in 1853 and 1876.