To connect with talents in Nanjing, you must first work in Nanjing (sign a labor contract with the company for one year or more and pay social security), and the company must open an account entrusted by personnel in Nanjing (it is just stipulated today that the company can not open an account, the details are unknown). In particular, a company can only connect with its registered permanent residence if it has three or more employee files at the same time (usually it will be transferred first and then settled).
Therefore, it is very difficult for you to settle down in Nanjing at present, unless you find a friend company to link with (meet the above premise), but when it comes to paying social security, you can pay it temporarily for a few months first, and then terminate the labor contract after the account is linked. If you have paid social security in Shanghai, there may be problems.