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MS Visual Studio .Net 2003 and SAP .Net Connector failure

Former Member
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Hi Gurus,

My environment is "SAP Client <-> firewall <-> SAP Server"

First scenario, SAP Client is SAPGui 6.20,

Cisco PIX Firewall,

SAP Server is SAP R/3 4.6C

Result -> I can connected via SAPGui to 3204/tcp successfully.

Second scenario, SAP Client is SAP .Net Connector & MS Visual Studio .Net 2003,

Cisco PIX Firewall,

SAP Server is SAP R/3 4.6C

Result -> I cannot connect via SAP .Net Connector to 3304/tcp as error below.

What's my mistake? Please recommend too.

Connect from SAP gateway to RFC server failed

Connect_PM GWHOST=, GWSERV=sapgw04, ASHOST=, SYSNR=04

LOCATION SAP-Gateway on host prdsapr3

ERROR connection to host, service sapgw04 timed out

TIME Thu Mar 10 16:17:12 2005


COMPONENT NI (network interface)


RC -12

MODULE nixxi.c

LINE 749




Choosak B.

Accepted Solutions (0)

Answers (1)

Answers (1)

Active Contributor
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RFC (and thus NCo) needs RFC port 3304 to be open. Likely this is blocked by the firewall. You can easily check with "telnet 3304".

Former Member
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The above error message is actually from the SAP gateway. This indicates that the .NET Connector has successfully passed through the firewall and reached the SAP Gateway, but the gateway failed to forward the call to the actual target, one of the SAP server processes running on the same host.

Usually, this problem may occur if there is a firewall that implements a NAT (Network Address Translator) between the RFC client and the SAP server. In this case, the SAP gateway receives an external IP-address from the client and mistakenly uses it as the address of the final destination without realizing that this external IP-address is invalid inside the firewall. Consequently, the attempt failed.

The solution to this problem is to add the external IP-address of the SAP server to the R/3 instance profile parameter gw/alternative_hostnames, for example in your case:

gw/alternative_hostnames =,

You need to restart the SAP Gateway after changing the profile parameter.

For details about this topic, please refer to the SAP note 148832.

Hope it helps,


Former Member
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We have exactly the same problem.

But according to our systemmanager, he is unable to set

the parameter gw/alternative_hostnames as it is not accepted.

Can this parameter be used in conjunction with netstat?

I know it would solve our problem because we were able to fix the problem by assigning an IP-alias with the external IP-address. but this was causing to much other problems.

Could you give me more detailed information on how to set this parameter?

Thank you in advance,