China was known to Byzantium through ambassadors from the Turks of central Asia. It was presumably from them that in the early seventh century the historian Theophylaktos Simokattes obtained detailed information about Chinese culture and imperial Chinese ceremonial. Trade was also done through intermediaries. Chinese silk was imported from Persia until, according to Prokopios of Caesarea and Theophanes of Byzantium, Justinian I obtained its secrets from Nestorian missionaries, who also managed to smuggle out some silkworm eggs. Nestorian communities were established in China, and in 1278 Andronikos II received an embassy of Nestorians from Beijing. Paper was a Chinese invention that found its way to Byzantium by the ninth century, via the Arabs who learned it from Chinese they captured in Samarkand in 751. Chinese awareness of Byzantium may have been chiefly through the Byzantine gold solidus, which circulated in China, as well as through Byzantine glass, enamels, and other luxury items.
(Source: «Historical Dictionary of Byzantium», by John H. Rosser)
Sino-Roman relations comprised the mostly indirect contact, flow of trade goods, information, and occasional travellers between the Roman Empire and Han Empire of China, as well as between the later Eastern Roman Empire and various Chinese dynasties. These empires inched progressively closer in the course of the Roman expansion into the ancient Near East and simultaneous Han Chinese military incursions into Central Asia. Mutual awareness remained low, and firm knowledge about each other was limited. Only a few attempts at direct contact are known from records. Intermediate empires such as the Parthians and Kushans, seeking to maintain lucrative control over the silk trade, inhibited direct contact between these two Eurasian powers. In 97 AD, the Chinese general Ban Chao tried to send his envoy Gan Ying to Rome, but Gan was dissuaded by Parthians from venturing beyond the Persian Gulf. Several alleged Roman emissaries to China were recorded by ancient Chinese historians. The first one on record, supposedly from either the Roman emperor Antoninus Pius or his adopted son Marcus Aurelius, arrived in 166 AD. Others are recorded as arriving in 226 and 284 AD, with a long absence until the first recorded Byzantine embassy in 643 AD.
The indirect exchange of goods on land along the Silk Road and sea routes included Chinese silk, Roman glassware and high-quality cloth. Roman coins minted from the 1st century AD onwards have been found in China, as well as a coin of Maximian and medallions from the reigns of Antoninus Pius and Marcus Aurelius in Jiaozhi in modern Vietnam, the same region at which Chinese sources claim the Romans first landed. Roman glassware and silverware have been discovered at Chinese archaeological sites dated to the Han period. Roman coins and glass beads have also been found in Japan.
In classical sources, the problem of identifying references to ancient China is exacerbated by the interpretation of the Latin term Seres, whose meaning fluctuated and could refer to several Asian peoples in a wide arc from India over Central Asia to China. In Chinese records, the Roman Empire came to be known as Daqin or Great Qin. Daqin was directly associated with the later Fulin (拂菻) in Chinese sources, which has been identified by scholars such as Friedrich Hirth as the Byzantine Empire. Chinese sources describe several embassies of Fulin arriving in China during the Tang dynasty and also mention the siege of Constantinople by the forces of Muawiyah I in 674–678 AD.