Form servlet mode or socket mode ?

Hi,
Our Apps 12i  uses 4 oc4j forms in Oracle Apps 12i. But within this month we have an issue with oc4j forms. From the opmn log files :

[libopmnoc4j] Process Ping Failed: default_group~forms~default_group~2 (1761098161:27798)
[libopmnoc4j] OC4J ping attempt timed out
[libopmnoc4j] Process Ping Failed: default_group~forms~default_group~3 (1761098162:27799)
[libopmnoc4j] OC4J ping attempt timed out
[libopmnoc4j] Process Ping Failed: default_group~forms~default_group~3 (1761098162:27799)
[libopmnoc4j] OC4J ping attempt timed out
[libopmnoc4j] Process Ping Failed: default_group~forms~default_group~2 (1761098161:27798)
[libopmnoc4j] OC4J ping attempt timed out