What I know: During the period leading up to the Opium Wars, trade into China from Europe was locked down to 13 buildings in Canton known as the 13 factories. European merchants were only permitted to do business in the 13 factories.

What I want to know: What title were the merchants who had authorization to deal with the europeans in the 13 factories called? Was there a title for these merchants who were allowed to deal with the outsiders? Was this even a special privilege, or could anyone walk into the 13 factories and strike a deal?

While we're at it, what's a better name than "the period leading up to the Opium Wars" for this period in Chinese history? That's obviously a eurocentric way to specify the time period, and I'd rather not do that.

I'm shamelessly crossposting this with the Chinese Language Stack Exchange, because I can't figure out which one is the "right" place to put this question. If there's a clear policy on which one I should have used, please accept my apologies in advance and educate me.