[jcifs] Timeout trying to open socket (probably no ACK to SYN) foraddress

Michael B Allen mba2000 at ioplex.com
Thu Nov 25 19:31:44 GMT 2004

Jens Schwitalla said:
> When I try to open a SMB Connection to a Windows 2003 Server or Windows XP
> PRO, i get the following Exception:
> jcifs.smb.SmbException: Timeout trying to open socket (probably no ACK to
> SYN)
> for address
> Does somebody know what that means?

When a socket is openend, a SYN packet is sent. If something is listening
at that address and port it will create a remote connection and reply with
an ACK. If nothing is listening at the address there will be no ACK and
the connection attempt will timeout. So it would appear that that address
is routable but nothing is listening. Note that jCIFS only supports
NetBIOS transport on port 139. Microsoft has started to move to raw
transport on port 445. Port 139 is still on by default but if your
security policy has it turned off JCIFS will not work. It's on the todo


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