100	DartFtp
512	A method is currently blocking the thread. Some PowerTcp methods are not reentrant. For example, if you set a timer and enter the Receive method with a Timeout, and attempt to enter the Receive method again, then this error is generated.
513	Connect method failed. Only one usage of each socket address (protocol/IP address/port) is normally permitted. This error  occurs if an application attempts to bind() a socket to an IP address/port that has already been used for an existing socket, or a socket that wasn't closed properly, or one that is still in the process of closing. For server applications that need to bind() multiple sockets to the same port number, consider using setsockopt(SO_REUSEADDR). Client applications usually need not call bind() at all - connect() will choose an unused port automatically. When the bind() is done to a wild-card address (involving ADDR_ANY), a WSAEADDRINUSE error could be delayed until the specific address is "committed".  This could happen in a later function such as connect(), listen(), WSAConnect(), or WSAJoinLeaf().
514	The requested address is not valid in its context. Normally results from an attempt to bind() to an address that is not valid for the local machine.  This may also result from  connect(), sendto(), WSAConnect(), WSAJoinLeaf(), or WSASendTo() when the remote address or port is not valid for a remote machine (e.g. address or port 0).
515	A socket operation encountered a dead network. This could indicate a serious failure of the network system (i.e. the protocol stack that the WinSock DLL runs over), the network interface, or the local network itself. 
516	A socket operation was attempted to an unreachable network. This usually means the local software knows no route to reach the remote host.
517	The connection has been broken due to "keep-alive" activity detecting a failure while the operation was in progress. May also be returned by setsockopt() if an attempt is made to set SO_KEEPALIVE on a connection that has already failed.
518	An established connection was aborted by the software in your host machine, possibly due to a data transmission timeout or protocol error. PowerTcp will close the connection when this error is encountered.
519	The virtual circuit was reset by the remote side executing a "hard" or "abortive" close. This normally results if the peer application on the remote host is suddenly stopped, the host is rebooted, or the remote host used a "hard close" (see setsockopt(SO_LINGER)) on the remote socket.  This error may also result if a connection was broken due to "keep-alive" activity detecting a failure while one or more operations are in progress.  Operations that were in progress fail with tcpNetworkReset.  Subsequent operations fail with tcpConnectionReset. PowerTcp closes the connection when this error is encountered.
520	Connect method failed. An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full. The socket cannot be connected.
521	Receive or Send method failed. The socket is not connected.
522	The connection has been dropped because of a network failure or because the peer system failed to respond. Also caused when Connect, Send, Receive, Fill or Close  methods are used with a Timeout parameter and the operation fails to complete within the specified number of milliseconds.
523	Connect method failed. No connection could be made because the target machine actively refused it.  This usually results from trying to connect to a service that is inactive on the foreign host - i.e. one with no server application running.
524	Connect method failed. A successful WSAStartup() call could not be made. This is the most serious failure of the network subsystem.
525	Connect method failed. No such host is known.  The name is not an official hostname or alias, or it cannot be found in the database(s) being queried. This error may also be returned for protocol and service queries, and means the specified name could not be found in the relevant database.
526	Connect method failed. This is usually a temporary error during hostname resolution and means that the local server did not receive a response from an authoritative server.  A retry at some time later may be successful.
527	Connect method failed. The requested name is valid and was found in the database, but it does not have the correct associated data being resolved for. The usual example for this is a hostname -> address translation attempt (using gethostbyname() or WSAAsyncGetHostByName()) which uses the DNS (Domain Name Server), and an MX record is returned but no A record - indicating the host itself exists, but is not directly reachable.
528	Miscellaneous error.
529	Parameter 1 of the method used is invalid or not appropriate.
530	Parameter 2 of the method used is invalid or not appropriate.
531	Parameter 3 of the method used is invalid or not appropriate.
532	Connect method failed. Some sort of non-recoverable error occurred during a database lookup. This may be because the database files (e.g. BSD-compatible HOSTS, SERVICES or PROTOCOLS files) could not be found, or a DNS request was returned by the server with a severe error.
533	Operation aborted by user.
534	A error occured in the protocol.
535	An error occured while performing a File I/O operation.