Unable to connect via adb on a firewalled Android device

Connecting from Linux, using an older adb (downloaded at tried 1.0.41 just to troubleshoot this - no difference, except that the messages now do include "Connection refused"), and the devices runs Android 9. This has worked fine literally for years, but all of a sudden, I can no longer connect to a device via TCP/IP. I can't think of anything that has changed. The device has a static IP (and I usually connect and disconnect multiple times per day), and I do run a firewall on it (AFWall+), which has never caused a problem in the past. $ ADB_TRACE=1 adb connect 192.168.0.2 main: 1915:140003988076352 | Handling commandline() adb_query: 1915:140003988076352 | adb_query: host:connect:192.168.0.2 _adb_connect: 1915:140003988076352 | _adb_connect: host:version WriteFdExactly: 1915:140003988076352 | writex: fd=3 len=4: 30303063 000c WriteFdExactly: 1915:140003988076352 | writex: fd=3 len=12: 686f73743a76657273696f6e host:version ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 got=4 4f4b4159 OKAY _adb_connect: 1915:140003988076352 | _adb_connect: return fd 3 adb_connect: 1915:140003988076352 | adb_connect: service host:connect:192.168.0.2 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 got=4 30303034 0004 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 got=4 30303230 0020 _adb_connect: 1915:140003988076352 | _adb_connect: host:connect:192.168.0.2 WriteFdExactly: 1915:140003988076352 | writex: fd=3 len=4: 30303161 001a WriteFdExactly: 1915:140003988076352 | writex: fd=3 len=26: 686f73743a636f6e6e6563743a313732 host:connect:192 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 got=4 4f4b4159 OKAY _adb_connect: 1915:140003988076352 | _adb_connect: return fd 3 adb_connect: 1915:140003988076352 | adb_connect: return fd 3 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=4 got=4 30303237 0027 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=39 ReadFdExactly: 1915:140003988076352 | readx: fd=3 wanted=39 got=39 756e61626c6520746f20636f6e6e6563 unable to connec unable to connect to 192.168.0.2:5555 Any ideas what might cause this?