Unable to connect to 636 secure port using LDAP library

[BANDANI MAHARANA]

Hi Team,
I am trying to connect to an Active directory server using 636 port for
secure connection. I am using the openldap library to establish the
connection.
Implementation is completed for insecure connection using 389 port. Below
is the code snippet I am using to establish the connection with ldap server
in 636 port.

LDAP * ldap_handler;
int return_value = ldap_initialize(ldap_handler, "ldaps://
TestServer.mylab.com:636"); //server url
     if (return_value == LDAP_SUCCESS) {
              cout<<"LDAP initialized successfully"; // this is successful
for me
             } else {
             cout<<"LDAP initialization failed";
            }
int return_value = ldap_set_option(*ldap_handler,
LDAP_OPT_PROTOCOL_VERSION, LDAP_VERSION3);
if(return_value == LDAP_SUCCESS) {
cout<<"success"; // this is successful for me
} else {
cout<<"failed";
}
const char * CACERT_FILE_PATH  = "certificate/mylab-TESTSERVER-CA.cer";
//certificate path
int return_value1 = ldap_set_option(*ldap_handler,
LDAP_OPT_X_TLS_CACERTFILE, CACERT_FILE_PATH);
if (return_value1 == LDAP_SUCCESS) {
} else {
// its failing here with error -1, and error string "Can't contact to LDAP
server"
}
int return_value = ldap_simple_bind_s(*ldap_handler, "mylab\administrator",
""pwd@1234");
if (return_value == LDAP_SUCCESS) {
//success
} else {
// its failing here with error -1, and error string "Can't contact to LDAP
server"
}
I have verified the same thing is working when connecting to 389 port.
Could you please suggest how to make this work for secure ldap connection
over ssl? Please provide some examples or references. It will be helpful
for me.

Thanks & Regards,
Bandani