Oracle Application Server cluster deployment:

Issue:
After configure discovery server topology in opmn.xml, still can not show cluster information. check opmn.log then found:
10/02/21 22:55:54 [ons-connect] Connection 2,server02,6200 connect (Connection refused)
10/02/21 22:55:55 [ons-connect] Connection 3,server02,6200 connect (Connection refused)

Analysis:
step1: telnet remote server
(0)oracle@server01:NO_SID: /u01/app/oracle/product/10.1.3/oas_01/opmn/conf
$ telnet server02 6200
Trying 192.168.184.12...
telnet: connect to address 192.168.184.12: Connection refused
telnet: Unable to connect to remote host: Connection refused

step2: check netstat and found the 6200 port bind to localhost, rather than server02
(1)oracle@server01:NO_SID: /u01/app/oracle/product/10.1.3/oas_01/opmn/conf
$ netstat -na | grep 6200
tcp        0      0 127.0.0.1:6200              0.0.0.0:*                   LISTEN

step3: check /etc/hosts file
$ cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
#::1    localhost6.localdomain6 localhost6
127.0.0.1       server01        localhost.localdomain   localhost
192.168.184.12  server02
192.168.184.11  server01

Solution:
1. update /etc/hosts on both nodes
$ cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
#::1    localhost6.localdomain6 localhost6
192.168.184.12  server02
192.168.184.11  server01
127.0.0.1       server01        localhost.localdomain   localhost

2. restart opmn on both nodes

3. telnet remote node
$ telnet server02 6200
Trying 192.168.184.12...
Connected to server02 (192.168.184.12).
Escape character is '^]'.

4. netstat status
$ netstat -na | grep 6200
tcp        0      0 192.168.184.11:6200         0.0.0.0:*                   LISTEN
tcp        0      0 192.168.184.11:6200         192.168.184.12:59483        ESTABLISHED

5. check cluster status
(0)oracle@server01:NO_SID: /u01/app/oracle/product/10.1.3/oas_01/opmn/conf
$ opmnctl @cluster status

Processes in Instance: oas_instance_01.server02
---------------------------------+--------------------+---------+---------
ias-component                    | process-type       |     pid | status
---------------------------------+--------------------+---------+---------
OC4JGroup:default_group          | OC4J:home          |    9117 | Init
ASG                              | ASG                |     N/A | Down
HTTP_Server                      | HTTP_Server        |    9116 | Alive

Processes in Instance: oas_instance_01.server01
---------------------------------+--------------------+---------+---------
ias-component                    | process-type       |     pid | status
---------------------------------+--------------------+---------+---------
OC4JGroup:default_group          | OC4J:home          |    9256 | Alive
ASG                              | ASG                |     N/A | Down
HTTP_Server                      | HTTP_Server        |    9255 | Alive