FileRead, text, D:\Downloads\Player.log
if ErrorLevel {
   MsgBox, Failed to read the file
   ExitApp
}
m := ""
needle := "Keepalive request https://login.playcaliber.com/ka/v1/keepalive response changed: "
while RegExMatch(text, "O)\Q" . needle . "\E\K\V+", m, m ? m.Pos + m.Len : 1)
   ( InStr(m[0], "user_id") && json := m[0] )

try AhkObj := JsonToAHK(json)
catch {
   MsgBox, Invalid JSON string
   ExitApp
}

for k, v in AhkObj.match.players
   MsgBox, % "user_id: "  . v.user_id . "`n"
           . "nickname: " . v.nickname

JsonToAHK(json, rec := false) {
   static doc := ComObjCreate("htmlfile")
        , __ := doc.write("<meta http-equiv=""X-UA-Compatible"" content=""IE=9"">")
        , JS := doc.parentWindow
   if !rec
      obj := %A_ThisFunc%(JS.JSON.parse(json), true)
   else if !IsObject(json)
      obj := json
   else if JS.Object.prototype.toString.call(json) == "[object Array]" {
      obj := []
      Loop % json.length
         obj.Push( %A_ThisFunc%(json[A_Index - 1], true) )
   }
   else {
      obj := {}
      keys := JS.Object.keys(json)
      Loop % keys.length {
         k := keys[A_Index - 1]
         obj[k] := %A_ThisFunc%(json[k], true)
      }
   }
   Return obj
}