This is the log of an EPICS 7.0.6 IOC with 'var CASDEBUG 3' when contacted by the ca_test unility:
7.0.6 client:
CAS: cast server msg of 48 bytes from addr 127.0.0.1:33835
CAS: Request from 127.0.0.1:33835 => cmmd=0 cid=0x1 type=1 count=13 postsize=0
CAS: Request from 127.0.0.1:33835 =>   available=0x0    N=1 paddr=(nil)
CAS: Request from 127.0.0.1:33835 => cmmd=6 cid=0x1 type=5 count=13 postsize=16
CAS: Request from 127.0.0.1:33835 =>   available=0x1    N=2 paddr=(nil)
CAS: Sending a udp message of 40 bytes
CAS: conn req from 127.0.0.1:58648
CAS: Request from 127.0.0.1:58648 => cmmd=0 cid=0x0 type=0 count=13 postsize=0
CAS: Request from 127.0.0.1:58648 =>   available=0x0    N=1 paddr=(nil)
CAS: Request from 127.0.0.1:58648 => cmmd=20 cid=0x0 type=0 count=0 postsize=8
CAS: Request from 127.0.0.1:58648 =>   available=0x0    N=2 paddr=(nil)
CAS: Request from 127.0.0.1:58648 => cmmd=21 cid=0x0 type=0 count=0 postsize=8
CAS: Request from 127.0.0.1:58648 =>   available=0x0    N=3 paddr=(nil)
CAS: Request from 127.0.0.1:58648 => cmmd=18 cid=0x1 type=0 count=0 postsize=16
CAS: Request from 127.0.0.1:58648 =>   available=0xd    N=4 paddr=(nil)
CAS: Sending a message of 48 bytes
CAS: Request from 127.0.0.1:58648 => cmmd=15 cid=0x7 type=0 count=2 postsize=0
CAS: Request from 127.0.0.1:58648 =>   available=0x1    N=1 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58648 => cmmd=15 cid=0x7 type=7 count=2 postsize=0
CAS: Request from 127.0.0.1:58648 =>   available=0x2    N=2 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58648 => cmmd=15 cid=0x7 type=14 count=2 postsize=0
CAS: Request from 127.0.0.1:58648 =>   available=0x3    N=3 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58648 => cmmd=15 cid=0x7 type=21 count=2 postsize=0
CAS: Request from 127.0.0.1:58648 =>   available=0x4    N=4 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58648 => cmmd=15 cid=0x7 type=28 count=2 postsize=0
CAS: Request from 127.0.0.1:58648 =>   available=0x5    N=5 paddr=0x7fca5c012178
CAS: Sending a message of 520 bytes
CAS: Request from 127.0.0.1:58648 => cmmd=12 cid=0x7 type=0 count=0 postsize=0
CAS: Request from 127.0.0.1:58648 =>   available=0x1    N=1 paddr=0x7fca5c012178
CAS: Sending a message of 16 bytes
CAS: nill message disconnect ( 8 bytes request )
CAS: Connection 22 Terminated

3.14.12 client:
CAS: Request from 127.0.0.1:52427 => cmmd=0 cid=0x1 type=1 count=13 postsize=0
CAS: Request from 127.0.0.1:52427 =>   available=0x0    N=1 paddr=(nil)
CAS: Request from 127.0.0.1:52427 => cmmd=6 cid=0x1 type=5 count=13 postsize=16
CAS: Request from 127.0.0.1:52427 =>   available=0x1    N=2 paddr=(nil)
CAS: Sending a udp message of 40 bytes
CAS: conn req from 127.0.0.1:58650
CAS: Request from 127.0.0.1:58650 => cmmd=0 cid=0x0 type=0 count=13 postsize=0
CAS: Request from 127.0.0.1:58650 =>   available=0x0    N=1 paddr=(nil)
CAS: Request from 127.0.0.1:58650 => cmmd=20 cid=0x0 type=0 count=0 postsize=8
CAS: Request from 127.0.0.1:58650 =>   available=0x0    N=2 paddr=(nil)
CAS: Request from 127.0.0.1:58650 => cmmd=21 cid=0x0 type=0 count=0 postsize=8
CAS: Request from 127.0.0.1:58650 =>   available=0x0    N=3 paddr=(nil)
CAS: Request from 127.0.0.1:58650 => cmmd=18 cid=0x1 type=0 count=0 postsize=16
CAS: Request from 127.0.0.1:58650 =>   available=0xd    N=4 paddr=(nil)
CAS: Sending a message of 48 bytes
CAS: Request from 127.0.0.1:58650 => cmmd=15 cid=0x8 type=0 count=2 postsize=0
CAS: Request from 127.0.0.1:58650 =>   available=0x1    N=1 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58650 => cmmd=15 cid=0x8 type=7 count=2 postsize=0
CAS: Request from 127.0.0.1:58650 =>   available=0x2    N=2 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58650 => cmmd=15 cid=0x8 type=14 count=2 postsize=0
CAS: Request from 127.0.0.1:58650 =>   available=0x3    N=3 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58650 => cmmd=15 cid=0x8 type=21 count=2 postsize=0
CAS: Request from 127.0.0.1:58650 =>   available=0x4    N=4 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58650 => cmmd=15 cid=0x8 type=28 count=2 postsize=0
CAS: Request from 127.0.0.1:58650 =>   available=0x5    N=5 paddr=0x7fca5c012178
CAS: Sending a message of 520 bytes
CAS: Request from 127.0.0.1:58650 => cmmd=12 cid=0x8 type=0 count=0 postsize=0
CAS: Request from 127.0.0.1:58650 =>   available=0x1    N=1 paddr=0x7fca5c012178
CAS: Sending a message of 16 bytes
CAS: nill message disconnect ( 8 bytes request )
CAS: Connection 3 Terminated

3.13.10 client:
pc12708> CAS: cast server msg of 32 bytes from addr 127.0.0.1:54966
CAS: Request from 127.0.0.1:54966 => cmmd=6 cid=0x0 type=1280 count=8 postsize=16
CAS: Request from 127.0.0.1:54966 =>   available=0x0    N=1 paddr=(nil)
CAS: Sending a udp message of 40 bytes
CAS: conn req from 127.0.0.1:58652
CAS: Request from 127.0.0.1:58652 => cmmd=20 cid=0x0 type=0 count=0 postsize=8
CAS: Request from 127.0.0.1:58652 =>   available=0x0    N=1 paddr=(nil)
CAS: Request from 127.0.0.1:58652 => cmmd=21 cid=0x0 type=0 count=0 postsize=8
CAS: Request from 127.0.0.1:58652 =>   available=0x0    N=2 paddr=(nil)
CAS: Request from 127.0.0.1:58652 => cmmd=18 cid=0x0 type=0 count=0 postsize=16
CAS: Request from 127.0.0.1:58652 =>   available=0x8    N=3 paddr=(nil)
CAS: Sending a message of 48 bytes
CAS: Request from 127.0.0.1:58652 => cmmd=15 cid=0x9 type=0 count=2 postsize=0
CAS: Request from 127.0.0.1:58652 =>   available=0x0    N=1 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58652 => cmmd=15 cid=0x9 type=7 count=2 postsize=0
CAS: Request from 127.0.0.1:58652 =>   available=0x1000000      N=2 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58652 => cmmd=15 cid=0x9 type=14 count=2 postsize=0
CAS: Request from 127.0.0.1:58652 =>   available=0x2000000      N=3 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58652 => cmmd=15 cid=0x9 type=21 count=2 postsize=0
CAS: Request from 127.0.0.1:58652 =>   available=0x3000000      N=4 paddr=0x7fca5c012178
CAS: Request from 127.0.0.1:58652 => cmmd=15 cid=0x9 type=28 count=2 postsize=0
CAS: Request from 127.0.0.1:58652 =>   available=0x4000000      N=5 paddr=0x7fca5c012178
CAS: Sending a message of 520 bytes
CAS: nill message disconnect ( 8 bytes request )
CAS: Connection 22 Terminated

The 3.13.10 lient never announces its version (cmd=0)!
I had to remove the client version check from camessage to make it work.
A 3.14.12 IOC shows the same messages.