Ssl – ldap_result: Can’t contact LDAP server (-1)

G'day,
I configured openldap-server machine which is running on port 636. I can also telnet to this port from another openldap-client machine. To secure the connection, I created a self-signed certificate on the server using this link enter link description here
and then copied the certificate file to the client.

I have made sure that SELinux is desabled on both machine and also the client /etc/openldap/ldap.conf file has the option TLS_REQCERT allow

The detailed configuration of client machine is:

# cat ldap.conf
URI ldap://ad.dfsi.dev:636
BASE dc=dfsi,dc=dev
TLS_CACERTDIR /etc/openldap/cacerts
TLS_REQCERT allow

and the nslcd file:

# cat /etc/nslcd.conf
tls_reqcert allow
ssl start_tls
tls_cacertdir /etc/openldap/cacerts
tls_reqcert allow

If I do not use SSL, then ldap client gets access to all ldap users. But, when I change the configuration to use TLS via authconfig-tui, ldaps://ad.xx.dev:636, then it fails.

The logs say that the client successfully connects to the server, but then then server drops the connection as shown here:

ldapsearch -x -d 1
ldap_create
ldap_sasl_bind
ldap_send_initial_request
ldap_new_connection 1 1 0
ldap_int_open_connection
ldap_connect_to_host: TCP ad.dfsi.dev:636
ldap_new_socket: 3
ldap_prepare_socket: 3
ldap_connect_to_host: Trying xx.xx.xx.xx:636
ldap_pvt_connect: fd: 3 tm: -1 async: 0
attempting to connect: 
connect success
ldap_open_defconn: successful
ldap_send_server_request
ber_scanf fmt ({it) ber:
ber_scanf fmt ({i) ber:
ber_flush2: 14 bytes to sd 3
ldap_result ld 0x7f8f75e1d150 msgid 1
wait4msg ld 0x7f8f75e1d150 msgid 1 (infinite timeout)
wait4msg continue ld 0x7f8f75e1d150 msgid 1 all 1
** ld 0x7f8f75e1d150 Connections:
* host: ad.dfsi.dev  port: 636  (default)
  refcnt: 2  status: Connected
  last used: Tue Nov 29 15:01:28 2016


** ld 0x7f8f75e1d150 Outstanding Requests:
 * msgid 1,  origid 1, status InProgress
   outstanding referrals 0, parent count 0
  ld 0x7f8f75e1d150 request count 1 (abandoned 0)
** ld 0x7f8f75e1d150 Response Queue:
   Empty
  ld 0x7f8f75e1d150 response count 0
ldap_chkResponseList ld 0x7f8f75e1d150 msgid 1 all 1
ldap_chkResponseList returns ld 0x7f8f75e1d150 NULL
ldap_int_select
read1msg: ld 0x7f8f75e1d150 msgid 1 all 1
ber_get_next
ldap_err2string
ldap_result: Can't contact LDAP server (-1)
ldap_free_request (origid 1, msgid 1)
ldap_free_connection 1 1
ldap_free_connection: actually freed

Running openssl shows that the client cannot find any certificates on the server, which is not reasonable because I have everything fixed there:

# openssl s_client -showcerts -connect ad.dfsi.dev:636 
CONNECTED(00000003)
140330386184096:error:140790E5:SSL routines:SSL23_WRITE:ssl handshake failure:s23_lib.c:184:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 247 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
---

nss-pam authconfg-tui generates its new CACERTDIR every time which overrides the previous configuration. Therefore, I have also put the certificate file in the /etc/openldap/cacerts folder.

My client machine is CentOS7 and server is Redhat ec2 instance.

Can anyone give me some hints to troubleshoot this?