2724420 - AS Java User Management - LDAPs connection fails - No connection to the ldap server - Connection reset - Best Practices for Investigation

During datasource configuration in AS Java User Management (UME), while trying to make LDAP over SSL (LDAPs) connection between SAP Portal and LDAP server, connection fails due to the following exception (partly in screen and full stacktrace in defaultTrace):

[...]
Please recheck the LDAP configuration Initialization of connection pool failed for USER
[...]
[EXCEPTION: No connection to the ldap server: Could not connect java.security.PrivilegedActionException: javax.naming.CommunicationException: <hostname>:636 [Root exception is java.net.SocketException: Connection reset]]#
[...]

and:

[...]
No connection to the directory server could be established
[EXCEPTION]
java.security.PrivilegedActionException: javax.naming.CommunicationException: <hostname>:636 [Root exception is java.net.SocketException: Connection reset]
[...]
Caused by: javax.naming.CommunicationException: <hostname>:636 [Root exception is java.net.SocketException: Connection reset]
 at com.sun.jndi.ldap.Connection.<init>(Connection.java:211)
[...]
 at com.sap.security.core.persistence.datasource.imp.LDAPDataSourceConnectionPool$Connector$1.run(LDAPDataSourceConnectionPool.java:1117)
[...]
Caused by: java.net.SocketException: Connection reset
 at java.net.SocketInputStream.read(SocketInputStream.java:167)
 at iaik.security.ssl.Utils.a(SourceFile:289)
 at iaik.security.ssl.B.e(SourceFile:350)
 at iaik.security.ssl.y.f(SourceFile:365)
 at iaik.security.ssl.n.b(SourceFile:730)
 at iaik.security.ssl.n.a(SourceFile:1501)
 at iaik.security.ssl.y.d(SourceFile:784)
 at iaik.security.ssl.SSLTransport.startHandshake(SourceFile:571)
 at iaik.security.ssl.SSLTransport.getInputStream(SourceFile:658)
 at iaik.security.ssl.SSLSocket.getInputStream(SourceFile:395)
 at com.sun.jndi.ldap.Connection.<init>(Connection.java:194)
[...] 

• SAP NetWeaver Application Server Java all versions
• Configuring LDAP as datasource in UME
• LDAP over SSL connection

LDAPS, tcpdump, tcp dump, SSL, TLS, Connection Reset, cipher suite, cipher suites, No connection to LDAP server , KBA , BC-JAS-SEC-UME , User Management Engine , BC-NET , Formerly used for network tests , BC-JAS-SEC-CPG , Cryptography , BC-CST-NI , Network Interface , Problem