There is only one that can truly be called a "channel" - the Silk Road. At that time, navigation technology was very underdeveloped, and monk Jianzhen risked his life by crossing east to Japan. Monk Xuanzang also went through hardships when he went to Tianzhu to seek Buddhist scriptures. Only the Silk Road truly became a gateway.
By the way, the name "Silk Road" is what Westerners, Arabs, and Persians call this passage. for they obtained their silk from this passage. If the Chinese named it, it would be called "Jewelry Road" because the Chinese obtained jewelry from this passage.