Here is a real life conversation (with IP, Hostname and ports masked) between the product I support and the z/OS based FTPS Server:
Our product uses Java FTP libraries from EnterpriseDT
---> SYST
215 MVS z/OS 011100 is the operating system for Connect:
---> PORT 111,111,111,111,11,111
200 PORT command successful.
---> LIST
150 Opening data connection.
Validating the server certificate when connecting to 'ftp.abc.com'.
Successfully validated the SSL server certificate when connecting to 'ftp.abc.com'
226 List complete. Closing data connection. 1 batches listed.
No input files found on server.
I don't understand the last two lines of the conversation. Why do I only receive a list and not the actual file?
Related
I've a problem with my FTP test server. I've installed and configured FileZilla server, It's listening for control connection on port 21, then it can provide passive mode data connection on ports between 50100 and 51100.
I'm trying a local connection 127.0.0.1:21 and retrieve the LIST of files and folders in the root FTP directory.
FileZilla Client: Works
FTP in MS-DOS: Works
TELNET in MS-DOS: Control connection and user authentication OK, then I switch to passive mode, and when I'm trying to retrieve files and folder with the command LIST It respond "Can't open data connection for transfer of "/"".
I've tried setting firewall rules for ports 50100-51100 and the FileZilla server. It's still not working.
You cannot retrieve files over FTP protocol using a Telnet client.
While you can simulate the FTP client by typing FTP commands on a Telnet console, you cannot do file transfers this way. It's because for file transfer you need a separate data transfer connection, what the Telnet client cannot do.
That's why the FTP server fails. In an active mode, it fails to connect back to your client machine, because there's nothing listening. In a passive more, it timeouts waiting for the client to connect to its data port.
I have googled and searched all over but I am still having trouble getting connected to a site using the ftpzilla
I am getting this read out when I try to connect to the server using the network connection wizard
Connecting to probe.filezilla-project.org
Response: 220 FZ router and firewall tester ready
USER FileZilla
Response: 331 Give any password.
PASS 3.9.0.6
Response: 230 logged on.
Checking for correct external IP address
Retrieving external IP address from
http://ip.filezilla-project.org/ip.php
Checking for correct external IP address IP 173.56.114.112
bhd-fg-bbe-bbc
Response: 200 OK
PREP 60010
Response: 200 Using port 60010, data token 1063172065
PORT 173,56,114,112,234,106
Response: 200 PORT command successful
LIST
Response: 150 opening data connection
Response: 503 Failure of data connection.
Server sent unexpected reply.
Connection closed
The weird thing is I only get this error for this particular server and the server I use for my personal site (namecheap.com) gives me no such error. Does anyone know why this may be happening? And please try not to point me to the network configuration wiki because I have read through that and I still am at this point.
PORT 173,56,114,112,234,106
....
Response: 503 Failure of data connection.
...
please try not to point me to the network configuration wiki
You are using active mode, that is the ftp client (FileZilla) waits for a connection from the server. Obviously the server can not connect to the client which indicates that something like a firewall restricts the connection.
Since according to your description this happens only with few servers, you either use only these servers with active mode or these servers are protected by firewalls which do not allow active mode. Have you tried with passive mode?
I had a similar issue connecting and made the following changes and had success.
Go to File>>>Site Manager>>>
For my site, I changed the Encryption to "Only use plain FTP(insecure)" and had success. May you find the same success.
I want to add support for the PORT command to my FTP server. I'm reading RFC 959, but I can't figure out when it's safe to connect to the FTP client. For example, consider this sequence:
PORT 127,0,0,1,34,34
LIST
Does the FTP client start listening before issuing the PORT command, or after issuing the LIST command? Because if the server attempts to connect to the client immediately after receiving PORT, it might fail because the client might not have started listening yet.
What does the specification say? Can the server connect immediately, or should it wait until after it receives the command that will make use of the data connection?
The server shouldn't connect to the client until it gets a command that requests a data transfer, such as LIST or RETR. See section 7 of RFC 959, which shows a typical sequence of operations (RFC's didn't have the formal MUST/MAY/SHOULD specifications in those early days).
However, since the port used in the PORT command is typically an ephemeral port, the client needs to open a socket to get the OS to assign a port number. This implies that by the time the PORT command is sent, the port would have to be open. However, it's possible that it might not yet have called listen().
Can you please tell me specifically what kind of data flows through which port during an FTP connection?
To be specific, I'd like to know whether contents of the directory and the server response codes flow through port 20.
FTP uses two types of connections: (1) the control connection (default port 21), which is used to send commands to the server and receive status codes back, and (2) the data connection (default port 20), which is used to transfer the content requested from the server: the content of a file or a directory listing, for example. I recommend to use a network protocol analyzer to see it with your own eyes. FTP specification RFC959 is written in an easily understandable manner, don't afraid to have a look at it.
Am trying to upload a file using libcurl in C. Data transmission is getting failed. Below is the log message.
How to fix this issue?
< 250 CWD command successful.
EPSV
Connect data stream passively
< 500 'EPSV': command not understood
disabling EPSV usage
PASV
< 227 Entering Passive Mode (x,x,x,x,193,152).
Trying x.x.x.x... * No route to host
couldn't connect to host
Closing connection #0
Couldn't connect to server
This means that when the FTP server opens a second port for your client to connect to, your client (libcurl) fails to reach it. It is most likely due to a firewall or other network equipment somewhere along the way that blocks your ability to do the request operation.
Alternative reasons could be a wrongly configured ftp server, but if it works for other users, that seems less likely.
Another reason for failure may be that you have an active firewall that doesn't know EPSV and thus gets confused by it and ruins it for you. Try without it by setting CURLOPT_FTP_USE_EPSV to 0.
You can try to the active approach instead (which is what most older style FTP clients do by default), which makes the client ask the server to connect back to you instead. You activate that in libcurl with CURLOPT_FTPPORT. (See the docs for exact details on how to use it.)