C:\Users\toshiba\Downloads\scrcpy-win64-v1.24>adb.exe devices -l
List of devices attached
16e806d00906           device product:olive_eea model:Redmi_8 device:olive transport_id:2


C:\Users\toshiba\Downloads\scrcpy-win64-v1.24>adb.exe tcpip 5555
restarting in TCP mode port: 5555

C:\Users\toshiba\Downloads\scrcpy-win64-v1.24>adb.exe connect 192.168.4.15
connected to 192.168.4.15:5555

C:\Users\toshiba\Downloads\scrcpy-win64-v1.24>scrcpy.exe
scrcpy 1.24 <https://github.com/Genymobile/scrcpy>
C:\Users\toshiba\Downloads\scrcpy-win64-v1.24\scrcpy-server: 1 file pushed, 0 skipped. 15.9 MB/s (41159 bytes in 0.002s)
[server] INFO: Device: Xiaomi Redmi 8 (Android 10)
INFO: Renderer: direct3d
INFO: Initial texture: 720x1520
WARN: Device disconnected
#############################################################################################
C:\Users\toshiba\Downloads\scrcpy-win64-v1.24>
Resolution
Sometimes a device has to tested without being USB connected to a PC. In that case, a valid TCP/IP connection can be used.

    First dock the device to have an USB connection
    Verify the device can be used and type 'adb devices'. The device should be listed.
    Define the adb TCP/IP port to be used, type the command 'adb TCPIP 5555'. Ensure the port is not blocked by switch or firewall and the device IP can be reached from PC network. So possibly use port 3389 (rdp) or 443 (https).
    Now start the adb network connection. Type 'adb connect 199.64.70.96:5555'
    There will be a 'connect' message by the adb command
    The USB connection can now be disconnected. All further adb commands now use the TCP/IP connection. For example, test with command 'adb logcat'


With the above, the device can be disconnected from USB but adb commands are still possible.

If multiple devices are connected, for example USB, Emulator and TCP/IP, the adb command must specify the desired device.

>adb devices -l
List of devices attached
17304D8189             device product:CT60 model:CT60 device:CT60-L0-C transport_id:12
199.64.70.96:3389      device product:CT60 model:CT60 device:CT60-L0-C transport_id:11


Then use the following command, to connect using the TCP/IP connected device.

adb -s 199.64.70.96:3389 shell


Use 'adb -d...' to execute against the only USB connected device. Use 'adb -e...' to connect to the only connection to an emulated device.