What country involved in a "Civil War" blockades its own ports?

Remember the "Trent Affair"? Wasn't that an international event? It almost caused England to declare War against the United States. Didn't England at that time reconize the authority of the Confederate diplomats which they had on board the Trent under England protection?

The Confederacy had trade relations with several other countries including letters of credit for military goods purchased abroad. That would seem like the most pracitical reconition of the Confederacy as an independant country.