Read https://github.com/appium/appium-remote-debugger/blob/master/development-notes.md
Once you could connect to the socket successfully, like below dump appears. com.apple.testmanagerd is testmanagerd. com.apple.CoreSimulator.SimDevice is simulators. Then, you can observe their exact communication protocol.
< 2020/05/25 00:20:00.491104 length=365 from=274610 to=274974
00 00 01 69 62 70 6c 69 73 74 30 30 d2 01 02 03 ...ibplist00....
0a .
5a 5f 5f 61 72 67 75 6d 65 6e 74 5a 5f 5f 73 65 Z__argumentZ__se
6c 65 63 74 6f 72 d3 04 05 06 07 08 09 5f 10 11 lector......._..
57 49 52 44 65 73 74 69 6e 61 74 69 6f 6e 4b 65 WIRDestinationKe
79 5f 10 11 57 49 52 4d 65 73 73 61 67 65 44 61 y_..WIRMessageDa
74 61 4b 65 79 5f 10 1b 57 49 52 41 70 70 6c 69 taKey_..WIRAppli
63 61 74 69 6f 6e 49 64 65 6e 74 69 66 69 65 72 cationIdentifier
4b 65 79 5f 10 24 45 42 34 43 39 42 37 46 2d 30 Key_.$EB4C9B7F-0
41 45 37 2d 34 31 32 39 2d 41 31 30 46 2d 37 32 AE7-4129-A10F-72
35 39 45 31 46 36 41 41 36 34 4f 10 73 7b 22 6d 59E1F6AA64O.s{"m
65 74 68 6f 64 22 3a 22 54 61 72 67 65 74 2e 64 ethod":"Target.d
69 73 70 61 74 63 68 4d 65 73 73 61 67 65 46 72 ispatchMessageFr
6f 6d 54 61 72 67 65 74 22 2c 22 70 61 72 61 6d omTarget","param
73 22 3a 7b 22 74 61 72 67 65 74 49 64 22 3a 22 s":{"targetId":"
70 61 67 65 2d 37 22 2c 22 6d 65 73 73 61 67 65 page-7","message
22 3a 22 7b 5c 22 72 65 73 75 6c 74 5c 22 3a 7b ":"{\"result\":{
7d 2c 5c 22 69 64 5c 22 3a 31 35 38 7d 22 7d 7d },\"id\":158}"}}
59 50 49 44 3a 36 35 30 36 31 5f 10 19 5f 72 70 YPID:65061_.._rp
63 5f 61 70 70 6c 69 63 61 74 69 6f 6e 53 65 6e c_applicationSen
74 44 61 74 61 3a 00 08 00 0d 00 18 00 23 00 2a tData:.......#.*
00 3e 00 52 00 70 00 97 01 0d 01 17 00 00 00 00 .>.R.p..........
00 00 02 01 00 00 00 00 00 00 00 0b 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 01 33 ...........3