Timeout during allocate while making RFC call

Question

I am trying to create a SAP RFC connection to a new system.

AFAIK the firewall (in this case to port 3321) is open.

I get this message at the client:

RFC_COMMUNICATION_FAILURE (rc=1): key=RFC_COMMUNICATION_FAILURE, message=
LOCATION    SAP-Gateway on host ax-swb-q06.prod.lokal / sapgw21
ERROR       timeout during allocate
TIME        Thu Jul 26 16:45:48 2018
RELEASE     753
COMPONENT   SAP-Gateway
VERSION     2
RC          242
MODULE      /bas/753_REL/src/krn/si/gw/gwr3cpic.c
LINE        2210
DETAIL      no connect of TP sapdp21 from host 10.190.10.32 after 20 sec
COUNTER     3
 [MSG: class=, type=, number=, v1-4:=;;;]

And this message on the SAP server

Any clue what needs to be done, to get RFC working?

Answer 1

it works in my case if ashost is the host name, and not an IP address!

Do not ask me why, but this fails:

Connection(user='x', passwd='...', ashost='10.190.10.32', sysnr='21', client='494')

But this works:

Connection(user='x', passwd='...', ashost='ax-swb-q06.prod.lokal', sysnr='21', client='494')

This is strange, since DNS resolution happens before TCP communication.

It seems that the ashost value gets used inside the connection. Strange. For most normal protocols (http, ftp, pop3, ...) this does not matter. Or you get at least a better error message.

Answer 2

With this little info no one can know what the issue is here. But it is something related to your network and SAP system configuration.

I guess your firewall does some network address translation (NAT) and the new IP behind the firewall does not match anymore with the known one. SAP is doing some own IP / host name security checks.

If not already done, check with opening the ports 3221, 3321 and 4821 in the firewall. Also check the SAP gateway configuration which IP addresses and host names are configured to be valid ones for it (look at what is traced in the beginning of the gateway trace file dev_rd at ABAP side).

Also consider if maybe the usage of a SAProuter would be the better option for your needs.