I fooled around a bit, and I think there are a few lose ends. Lets update the examples in docs/interop/qmp-spec.txt to show the current greeting (section 3.1) and how to accept a capability (section 3.2). The capability negotiation documentation could use some polish. I'll post a patch.
Talking to a QMP monitor that supports OOB: $ socat UNIX:test-qmp READLINE,history=$HOME/.qmp_history,prompt='QMP> ' {"QMP": {"version": {"qemu": {"micro": 50, "minor": 12, "major": 2}, "package": "v2.12.0-1703-gb909799463"}, "capabilities": ["oob"]}} QMP> { "execute": "qmp_capabilities", "arguments": { "oob": true } } {"error": {"class": "GenericError", "desc": "Parameter 'oob' is unexpected"}} QMP> { "execute": "qmp_capabilities", "arguments": { "enable": ["oob"] } } {"return": {}} QMP> { "execute": "query-qmp-schema" } {"error": {"class": "GenericError", "desc": "Out-Of-Band capability requires that every command contains an 'id' field"}} Why does every command require 'id'? Talking to a QMP monitor that doesn't support OOB: {"QMP": {"version": {"qemu": {"micro": 50, "minor": 12, "major": 2}, "package": "v2.12.0-1703-gb909799463"}, "capabilities": []}} QMP> { "execute": "qmp_capabilities", "arguments": { "enable": ["oob"] } } {"error": {"class": "GenericError", "desc": "This monitor does not support Out-Of-Band (OOB)"}} QMP> { "execute": "qmp_capabilities" } {"return": {}} QMP> { "execute": "query-kvm" } {"return": {"enabled": true, "present": true}} QMP> { "execute": "query-kvm", "control": { "run-oob": true } } {"error": {"class": "GenericError", "desc": "Please enable Out-Of-Band first for the session during capabilities negotiation"}} Telling people to enable OOB when that cannot be done is suboptimal. More so when it cannot be used here anyway. I'll post a patch.