Verified with PXC 5.6.22. 

 [root@percona1 ~]# tail -f /data/myisam/percona1_error.log
2015-05-12 12:00:25 15798 [Note] /usr/sbin/mysqld: ready for connections.
Version: '5.6.22-72.0-56'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  Percona XtraDB Cluster (GPL), Release rel72.0, Revision 978, WSREP version 25.8, wsrep_25.8.r4150
2015-05-12 12:00:25 15798 [Note] WSREP: Receiving IST: 78 writesets, seqnos 299786-299864
2015-05-12 12:00:38 15798 [Note] WSREP: IST received: fadf885a-490b-11e4-9e13-27f574d828b6:299864
2015-05-12 12:00:38 15798 [Note] WSREP: 2.0 (percona1): State transfer from 0.0 (percona2) complete.
2015-05-12 12:00:38 15798 [Note] WSREP: Shifting JOINER -> JOINED (TO: 299864)
2015-05-12 12:00:38 15798 [Note] WSREP: Member 2.0 (percona1) synced with group.
2015-05-12 12:00:38 15798 [Note] WSREP: Shifting JOINED -> SYNCED (TO: 299864)
2015-05-12 12:00:38 15798 [Note] WSREP: Synchronized with group, ready for connections
2015-05-12 12:00:38 15798 [Note] WSREP: wsrep_notify_cmd is not defined, skipping notification.
^C
[root@percona1 ~]# ps -ef|egrep "mysql|xbs|socat"
root     15243     1  0 11:59 pts/0    00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/data/myisam --pid-file=/data/myisam/percona1.pid
mysql    15798 15243 58 11:59 pts/0    00:00:41 /usr/sbin/mysqld --basedir=/usr --datadir=/data/myisam --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --wsrep-provider=/usr/lib64/libgalera_smm.so --log-error=/data/myisam/percona1_error.log --open-files-limit=65535 --pid-file=/data/myisam/percona1.pid --wsrep_start_position=fadf885a-490b-11e4-9e13-27f574d828b6:299786
mysql    16048     1  0 12:00 ?        00:00:00 socat -u TCP-LISTEN:4444,reuseaddr stdio
mysql    16049     1  0 12:00 ?        00:00:00 xbstream -x

Also with STOP/START IST

[root@percona3 ~]# ps -ef|egrep "mysql|xbs|socat"
root      3489     1  0 11:11 pts/0    00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/data/myisam --pid-file=/data/myisam/percona3.pid
mysql     4104  3489  0 11:11 pts/0    00:01:25 /usr/sbin/mysqld --basedir=/usr --datadir=/data/myisam --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --wsrep-provider=/usr/lib64/libgalera_smm.so --log-error=/data/myisam/percona3_error.log --open-files-limit=65535 --pid-file=/data/myisam/percona3.pid --wsrep_start_position=fadf885a-490b-11e4-9e13-27f574d828b6:299786
root     15343  3258  0 13:37 pts/0    00:00:00 egrep mysql|xbs|socat
[root@percona3 ~]# service mysql stop
Shutting down MySQL (Percona XtraDB Cluster)..... SUCCESS!
[root@percona3 ~]# service mysql start
Starting MySQL (Percona XtraDB Cluster)..........State transfer in progress, setting sleep higher
. SUCCESS!
[root@percona3 ~]# ps -ef|egrep "mysql|xbs|socat"
root     15396     1  0 13:40 pts/0    00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/data/myisam --pid-file=/data/myisam/percona3.pid
mysql    15949 15396 24 13:40 pts/0    00:00:18 /usr/sbin/mysqld --basedir=/usr --datadir=/data/myisam --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --wsrep-provider=/usr/lib64/libgalera_smm.so --log-error=/data/myisam/percona3_error.log --open-files-limit=65535 --pid-file=/data/myisam/percona3.pid --wsrep_start_position=fadf885a-490b-11e4-9e13-27f574d828b6:299864
mysql    16225     1  0 13:40 ?        00:00:00 socat -u TCP-LISTEN:4444,reuseaddr stdio
mysql    16226     1  0 13:40 ?        00:00:00 xbstream -x
root     16272  3258  0 13:41 pts/0    00:00:00 egrep mysql|xbs|socat