IBM Support

Gentran:Server FTP communication - When sending larger files receive error message "Unknown Explanation".

Technote (troubleshooting)


CTimeoutSocket receiving...
CTimeoutSocket::SetTimeOut() called.
CTimeoutSocket timer message received.
CTimeoutSocket cancelling socket call due to timeout.
CTimeoutSocket::KillTimeOut() called.
CTimeoutSocket receive complete.
ERROR: CSocket::Receive failed: Unknown Explanation

ERROR: CSocket::Accept failed: Unknown Explanation

ERROR: CSocket::Receive failed: The descriptor is not a socket

Found from network Capture and Server capture that a delay was occuring on finding responding packets.
Sniffer traces show SYN timeout and TCP FINS


FTP logon & Directory declaration is happening. When the scripting is requesting a list or nlst or dir the comm log shows a 60 second lag and then this timeout and failed messages appear.


Operating System, NIC or Network causing issue.

Diagnosing the problem

Create a capture for server to network during large file upload. Ask VAN to also create a capture. In this issue the delay occurred when request was made to send next packet.

Resolving the problem

Unfortunately, this is not a Gentran:Server for Windows issue. However here is a list of suggestions:

a. Log into the server using the Gentran Services Windows Account. Check that server operating system is functioning correctly.

b. Check if NIC drivers have been changed recently or need updated

c. Check that DHCP or static IP address is working correctly.

d. If Operation system has been changed, it's possible that the OS reacts differently to the FTP scripting and Passive mode is needed (vs Active mode).
1. Engage the VAN team for IP address for Passive mode connection info.
2. Update the mailbox properties to use the new address given AND check the box for PASV.

Product Alias/Synonym


Document information

More support for: Sterling Gentran:Server for Microsoft Windows

Software version: 5.1, 5.2, 5.3, 5.3.1

Operating system(s): Windows

Software edition: All Editions

Reference #: 1616154

Modified date: 15 April 2015

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