Amartya Sen has an article in New York Review of Books on the 2000 year old relation between China and India. Since ancient times China has exported its goods to India and India exported Buddhism and Mathematics to China.
As it happens, relations between China and India almost certainly began with trade, not with Buddhism. Some two thousand years ago the consumption habits of Indians, particularly of rich Indians, were radically influenced by innovations from China. A treatise on economics and politics by the great Sanskrit scholar Kautilya, first written in the fourth century BCE, though revised a few centuries later, gives a special place to “silk and silk-cloth from the land of China” among “precious articles” and “objects of value.” In the ancient epic Mahabharata there are references to Chinese fabric or silk (cinamsuka) being given as presents, and there are similar references in the ancient Laws of Manu.
Chinese records show that several Indian astronomers and mathematicians held high positions in the Astronomical Bureau at the Chinese capital during this period. Not only did one of them, Gautama, became president of the Board of Astronomy in China, he also produced the great Chinese compendium of astronomy, Kaiyvan Zhanjing, an eighth-century scientific classic. He adapted a number of Indian astronomical works for publication in Chinese, among them the Jiuzhi li, which draws on a particular planetary calendar in India and is clearly based on a classical Sanskrit text, produced around 550 CE by the mathematician Varahamihira. This work is mainly an algorithmic guide to computation, estimating, for example, the duration of eclipses based on the diameter of the moon and other relevant parameters. The techniques involved drew on methods established by Aryabhata in the late fifth century, and then further developed by his followers in India, including Varahamihira and Brahmagupta. [Passage to China]
One of the travelers Fax-ian who came to India in 401 AD was impressed by the medical facilities in Bihar and wrote
All the poor and destitute in the country…and all who are diseased, go to these houses, and are provided with every kind of help, and doctors examine their diseases. They get the food and medicines which their cases require, and are made to feel at ease; and when they are better, they go away of themselves.
In the 21st century Bihar both the doctors and patients are in trouble.