East Asia being defined as the countries of the Pacific Rim (China, Japan, Vietnam, Indonesia, etc). Not counting Russia.
In 166 AD, an envoy from the Roman Empire was received by the Han emperor Huan in Luoyang, China's then capital. Prior to that time, the Romans and the Chinese had been vaguely aware of each other through Silk Road intermediaries, but they had never had direct contact before. In fact, Roman and Chinese trade goods made the journey between the two empires long before any person went the full way.