What was the purpose of President Lincoln ordering a naval blockade of the South?

The attempt to blockade Southern ports and cause the Confederacy great economic harm was based on the once discarded Winfield Scott plan called the Anaconda Plan. The idea was sound enough, however, there were logistical problems involved with a really effective blockade. There were simply too many ports of entry, night time privateers escaped scrutiny and there was not enough Union warships to handle the project. It is also important to remember that ship to ship communications in 1861 were primitive. And, ship to shore communications also lacked the technology to communicate. Also, the threat of Confederate river and sea mines caused any number of problems.