This is the minimal code needed to create a FTP server:
In this case a server that listens on port 21, servers up data from c:\temp, and allows anyone to access it
FtpServer server = new FtpServer();
server.AddListener(new NonsecureTcpListener(FtpServer.DEFAULT_NONSECURE_PORT));
server.FileSystem = new DiskFileSystem("c:\\temp");
server.SecurityProvider = new OpenSecurityProvider();
server.Start();
// ...
server.Stop();