420 TCP Read Error
(Last modified: 22Feb2003)
This document (10080200) is provided subject to the disclaimer at the end of this document.
fact
meNovell GroupWise Internet Agent 6.0 (GWIA)
Novell GroupWise Internet Agent 5.5 EP (GWIA)
Formerly TID 2910937
symptom
DMN: Send Failure: 420 TCP read error
Response: 420 TCP write error
420 TCP Read Error and 420 Write on the GWIA
550 Host unknown
The GWIA Gateway was reporting error "420 TCP Read Error" when attempting to send an outbound message. After increasing the daemon's send threads to 10, the gateway still reported the error.
cause
On an outbound message, the GWIA Gateway and Daemon processes take the following steps:
1. The gateway (GWIA) picks the file up from the <domain>\WPGATE\GWIA\WPCSOUT\<gatewayID>\0-7 directory, converts the message to the SMTP format specified in the GWIA.CFG file, and places the converted message in the SEND directory.
2. The daemon (GWIA) processes the file in the SEND directory, examines the address (user@host) and makes a call to NetWare's TCP/IP services to resolve the domain name (hostname) to an IP address using DNS (RESOLV.CFG or HOSTS file).
- If the daemon resolves the IP address, it attempts to connect to it on port 25.
- If the daemon fails to resolve the IP address, a "550 Host unknown" is returned.
3. The daemon then attempts to connect to the IP address.
- If it is able to connect, it begins to process Read and Write commands.
- If it is unable to connect, a "450 Host down" is returned.
4. The daemon processes Read and Write commands until they are completed (the message is actually transferred). It will then disconnect.
5. If there are any problems with the Read and Write commands, the Daemon thread will wait until the timeout period and then disconnect (5 minutes by default). At this time either a 420 Read or 420 Write error will be returned.
6. After a 400-level error, the message is queued to the DEFER directory to be processed again at a later time, hopefully when the connection is available to read and write correctly.
Note: A low percentage of 420 Read and Write error messages can be expected on a regular basis. If a high percentage (errors/messages sent) of 420 errors occur, there may be problems with the Internet connection or TCP/IP packet fragmentation.
In one case the cable was moved to a different port in the switch and this corrected the issue.
Note: See TID 10010463 and the GWIA Gateway manual for details on deferred messages.
note
1. To determine whether the connection is having a problem, telnet to the IP address on port 25 from a workstation using the following syntax:
telnet xxx.xxx.xxx.xxx 25
Once the connection has been made you can type helo or some other smtp commands to determine if the connection was accepted by the mail server. To end type "quit."
fix
Resolve network issue with ISP to allow mail servers to communicate without timing out.
In some cases increasing the send and receive threads under SMTP / MIME setting in the properties of the GWIA resolves this issue. Once the setting have been changed the GWIA will need to be restarted.
document
| Document Title: | 420 TCP Read Error |
| Document ID: | 10080200 |
| Solution ID: | NOVL87124 |
| Creation Date: | 12Feb2003 |
| Modified Date: | 22Feb2003 |
| Novell Product Class: | Groupware |
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