Topic: FTPS data port failure.
I am looking for some assistance with an FTPS client app I am writing.
I am having a problem, which I cannot determine if this is a client or server issue. But here are a few key points:
- Our test server running an MS FTPS service can be connected to with the FileZilla app.
- When I connect with a client app I am writing, the control port connects fine and communicates,
- The handshake times out only on the passive connection handshake.
I can see it is not the TCP/IP connect call that is timing out.
It is in fact the handshake: "result = wolfSSL_connect(m_dataSsl);" call that times out.
- I can use both FileZilla and the client app I'm developing to connect to a customer's server.
Therefore it would be something about this test server... And yet, the FileZilla client app connects fine.
This also tells me it is not a firewall issue, And I have to assume it's something in the way WolfSSL lib is sending the handshake.
I have attached a WireShark log. Lines 4 and 5 are the handshake for the control connection (port 990)
Line 37 is the client sending the hello for the passive data connection, however the server never responds.
Can anyone give me a clue to figure out why the server is happy with the handshake on the control port (port 990), but doesn't like the handshake on the passive data port (port range 20001 to 21000) ?
I have already confirmed that session resumption is disabled on our server.
Any advice is appreciated.
<Code shown is not to scale>