Not sure how you can mention Nanjing without Yangzhou, Suhzou and Hangzhou. Together they basically encircle modern Shanghai.
It is documented in the Tang Dynasty that boats from Japan bound for China would sometimes land along the coast of Jiangsu then the occupants would move inland. IIRC if riverborne the first small town they would reach was Nantong, and the first major town up-river would be Yangzhou. Approaching overland, they would no doubt be escorted directly to Yangzhou. Jiangsu seems to have essentially consisted of a vast canal network and agricultural lands. Presumably the Koreans hit Shandong (dodging pirates), and the South (India) and Southeast Asians (Philippines, Sumatra, Borneo, Vietnam, Thailand, Malaysia) hit Guangdong or Guangxi. Fujian, in the middle of these landing zones, had sometimes in history a flourishing trading culture, with Quanzhou IIRC the town from which historically attested Chinese Zhenghe expeditions departed as far as Southeast Asia, India, Arabia and Africa, and global religious communities are attested.
Zhenghe was himself a sufi muslim Eunuch born inland in the Himalayas at ~2200m altitude, last bastion of the purged Mongol-era ruling family of Yunnan, descended from the pre-Mongol invasion Emir of Bokhara, Uzbekistan, and through his family thought to be fluent in Persian, which was then something of a pan-regional lingua franca.
Despite this, the modern Chinese state narrative is that everyone is flat "Chinese". Further leaning on the Central Asian cultural nexus, it is worth re-stating that Li Bai, arguably classical China's most famous poet, was actually born in Kyrgyzstan and after moving to China lived primarily in the then-remote province of Sichuan, quite peripheral to northern Chinese culture, in fact the province was contemporaneously successfully invaded by the Tibeto-Burman rival kingdom of Nanzhao, whose still visible legacy includes undeniably Hindu grottoes carved in Sanskrit.
If you want to learn history, don't look at modern textbooks.