CRS-0184: Cannot communicate with the CRS daemon CRS-4639: Could not contact Oracle High Availability Services

After restarted server and I was starting ASM instance appear error :

CRS-0184: Cannot communicate with the CRS daemon 
CRS-4639: Could notcontact Oracle High Availability Services

I will show you how to solve this, there may be many reasons I'll write here which is very often.
First of all check services and if they aren't started try to start:

crs_stat -t
CRS-4639: Could not contact Oracle High Availability Services

CRS-4000: Command Status failed, or completed with errors.

crsctl start resource ora.cssd
 

If there still error then try loging with root user and remove all files under /tmp/.oracle or /var/tmp/.oracle, because sometimes when CRS server reboot it try to create sockets under /tmp/.oracle or /var/tmp/.oracle and there are already previous socket files...which are protecting to create new sockets. restart CRS on faulty node or even reboot that machine!.

if it is not enough then check $ORACLE_HOME/bin/oracle executable file permissions it must have:

[oracle@oel5 ~]$ ls -lrt $ORACLE_HOME/bin/oracle
-rwsr-s--x 1 oracle dba 210824714 May 21  2012 /u0/app/oracle/product/11.2.0/dbhome_1/bin/oracle

If it is not same permission as shown above change it with:

chmod 6751 $ORACLE_HOME/bin/oracle

If there is still errors try

crsctl enable has
crsctl start has

If the errors still try with root

[root@oel5 ~]# /etc/init.d/syslog start
[root@oel5 ~]# /etc/init.d/ohasd start

I think it will be helpful for you,
thank you.