Thanks for flagging this. I have not yet tested the BYOS flow but we need to change the API request to point to the BYOS server and make any changes necessary to support the API of the BYOS server.

I will leave this issue open as I hope to get to this in a couple of weeks but you can give this piece of code to an LLM tool and see if it can adapt it for your BYOS server.

trmnl-koreader/trmnl.koplugin/main.lua

Lines 203 to 354 in 1ce27dd

    
           --[[-- 
        
           Fetch screen metadata from TRMNL API. 
        
           Makes HTTP GET request to /api/display endpoint with headers: 
        
           - access-token: User's API key 
        
           - battery-voltage: Device battery percentage 
        
           - png-width/png-height: Screen dimensions in pixels 
        
           - rssi: WiFi signal strength (hardcoded to 0 for now) 
        
           - User-Agent: Plugin version string 
        
           @treturn table|nil Decoded JSON response table, or nil on error 
        
           ]] 
        
           function TrmnlDisplay:fetchScreenMetadata() 
        
               if not self.settings.api_key or self.settings.api_key == "" then 
        
                   self:showError("Please configure your TRMNL API key first.") 
        
                   return nil 
        
               end 
        
               -- LuaSocket libraries for HTTP/HTTPS requests 
        
               local http = require("socket.http") -- HTTP protocol 
        
               local https = require("ssl.https")  -- HTTPS/TLS protocol 
        
               local ltn12 = require("ltn12")      -- Streaming data I/O filters 
        
               local JSON = require("json")        -- JSON parsing 
        
               -- ltn12.sink.table accumulates response body into a Lua table 
        
               local sink = {} 
        
               local request_url = self.settings.base_url .. "/api/display" 
        
               -- Get device information for API headers 
        
               -- Device:hasBattery() checks if device has battery capability 
        
               -- Device:getPowerDevice() returns power device object with getCapacity() method 
        
               local battery_voltage = "0" 
        
               if Device:hasBattery() then 
        
                   local powerd = Device:getPowerDevice() 
        
                   battery_voltage = tostring(powerd:getCapacity()) -- Returns 0-100 percentage 
        
               end 
        
               -- Screen:getWidth()/getHeight() return pixel dimensions 
        
               -- TRMNL uses this to generate appropriately sized images 
        
               local png_width = tostring(Screen:getWidth()) 
        
               local png_height = tostring(Screen:getHeight()) 
        
               logger.info("TRMNL: Fetching screen from", request_url) 
        
               logger.dbg("TRMNL: Screen dimensions:", png_width, "x", png_height) 
        
               -- Build HTTP request table (LuaSocket format) 
        
               local request = { 
        
                   url = request_url, 
        
                   method = "GET", 
        
                   headers = { 
        
                       ["access-token"] = self.settings.api_key,  -- TRMNL API authentication 
        
                       ["battery-voltage"] = battery_voltage,     -- Device battery level 
        
                       ["png-width"] = png_width,                 -- Screen width in pixels 
        
                       ["png-height"] = png_height,               -- Screen height in pixels 
        
                       ["rssi"] = "0",                            -- WiFi signal strength (TODO: implement) 
        
                       ["User-Agent"] = self.settings.user_agent, -- Plugin identification 
        
                   }, 
        
                   sink = ltn12.sink.table(sink),                 -- Response body stored in 'sink' table 
        
                   -- SSL/TLS configuration for HTTPS 
        
                   protocol = "any",                              -- Accept any SSL/TLS version 
        
                   options = { "all", "no_sslv2", "no_sslv3" },   -- Disable insecure SSL versions 
        
                   verify = "none",                               -- Skip certificate verification (required for Kindles with outdated cert stores) 
        
               } 
        
               -- Choose HTTP or HTTPS based on URL scheme 
        
               local httpx = request_url:match("^https://") and https or http 
        
               local success_code, status_code = httpx.request(request) 
        
               logger.dbg("TRMNL: Success code:", success_code) 
        
               logger.dbg("TRMNL: HTTP status code:", status_code) 
        
               if not success_code or success_code ~= 1 then 
        
                   logger.err("TRMNL: Request failed - success code:", success_code) 
        
                   local context = "Network error - check WiFi connection\nURL: " .. request_url 
        
                   self:showError(T(_("Failed to reach TRMNL API (code: %1)"), tostring(success_code)), context) 
        
                   return nil 
        
               end 
        
               if status_code ~= 200 then 
        
                   logger.err("TRMNL: API returned HTTP", status_code) 
        
                   local context_msg 
        
                   if status_code == 401 or status_code == 403 then 
        
                       context_msg = "Check your API key in settings" 
        
                   elseif status_code == 404 then 
        
                       context_msg = "Endpoint not found - verify base URL" 
        
                   elseif status_code >= 500 then 
        
                       context_msg = "Server error - try again later" 
        
                   else 
        
                       context_msg = "HTTP " .. tostring(status_code) 
        
                   end 
        
                   self:showError("API request failed", context_msg) 
        
                   return nil 
        
               end 
        
               local response_body = table.concat(sink) 
        
               logger.dbg("TRMNL: Received response:", response_body:sub(1, 200)) 
        
               local ok, response = pcall(JSON.decode, response_body) 
        
               if not ok or not response then 
        
                   logger.err("TRMNL: Failed to parse JSON response") 
        
                   return nil 
        
               end 
        
               return response 
        
           end 
        
           function TrmnlDisplay:downloadImage(image_url, filepath) 
        
               local http = require("socket.http") 
        
               local https = require("ssl.https") 
        
               local ltn12 = require("ltn12") 
        
               logger.info("TRMNL: Downloading image from", image_url) 
        
               local file = io.open(filepath, "wb") 
        
               if not file then 
        
                   logger.err("TRMNL: Failed to open file for writing:", filepath) 
        
                   return false 
        
               end 
        
               local request = { 
        
                   url = image_url, 
        
                   sink = ltn12.sink.file(file), 
        
                   headers = { 
        
                       ["User-Agent"] = self.settings.user_agent, 
        
                   }, 
        
                   -- SSL/TLS configuration (same as API request) 
        
                   protocol = "any", 
        
                   options = { "all", "no_sslv2", "no_sslv3" }, 
        
                   verify = "none", -- Skip certificate verification (required for Kindles) 
        
               } 
        
               local httpx = image_url:match("^https://") and https or http 
        
               local success_code, status_code = httpx.request(request) 
        
               logger.dbg("TRMNL: Image download success code:", success_code) 
        
               logger.dbg("TRMNL: Image download HTTP status:", status_code) 
        
               if not success_code or success_code ~= 1 then 
        
                   logger.err("TRMNL: Image download failed - success code:", success_code) 
        
                   os.remove(filepath) 
        
                   return false 
        
               end 
        
               if status_code ~= 200 then 
        
                   logger.err("TRMNL: Image download failed - HTTP", status_code) 
        
                   os.remove(filepath) 
        
                   return false 
        
               end 
        
               logger.info("TRMNL: Image downloaded successfully") 
        
               return true 
        
           end

	--[[--
	Fetch screen metadata from TRMNL API.

	Makes HTTP GET request to /api/display endpoint with headers:
	- access-token: User's API key
	- battery-voltage: Device battery percentage
	- png-width/png-height: Screen dimensions in pixels
	- rssi: WiFi signal strength (hardcoded to 0 for now)
	- User-Agent: Plugin version string

	@treturn table\|nil Decoded JSON response table, or nil on error
	]]
	function TrmnlDisplay:fetchScreenMetadata()
	if not self.settings.api_key or self.settings.api_key == "" then
	self:showError("Please configure your TRMNL API key first.")
	return nil
	end

	-- LuaSocket libraries for HTTP/HTTPS requests
	local http = require("socket.http") -- HTTP protocol
	local https = require("ssl.https") -- HTTPS/TLS protocol
	local ltn12 = require("ltn12") -- Streaming data I/O filters
	local JSON = require("json") -- JSON parsing

	-- ltn12.sink.table accumulates response body into a Lua table
	local sink = {}
	local request_url = self.settings.base_url .. "/api/display"

	-- Get device information for API headers
	-- Device:hasBattery() checks if device has battery capability
	-- Device:getPowerDevice() returns power device object with getCapacity() method
	local battery_voltage = "0"
	if Device:hasBattery() then
	local powerd = Device:getPowerDevice()
	battery_voltage = tostring(powerd:getCapacity()) -- Returns 0-100 percentage
	end

	-- Screen:getWidth()/getHeight() return pixel dimensions
	-- TRMNL uses this to generate appropriately sized images
	local png_width = tostring(Screen:getWidth())
	local png_height = tostring(Screen:getHeight())

	logger.info("TRMNL: Fetching screen from", request_url)
	logger.dbg("TRMNL: Screen dimensions:", png_width, "x", png_height)

	-- Build HTTP request table (LuaSocket format)
	local request = {
	url = request_url,
	method = "GET",
	headers = {
	["access-token"] = self.settings.api_key, -- TRMNL API authentication
	["battery-voltage"] = battery_voltage, -- Device battery level
	["png-width"] = png_width, -- Screen width in pixels
	["png-height"] = png_height, -- Screen height in pixels
	["rssi"] = "0", -- WiFi signal strength (TODO: implement)
	["User-Agent"] = self.settings.user_agent, -- Plugin identification
	},
	sink = ltn12.sink.table(sink), -- Response body stored in 'sink' table
	-- SSL/TLS configuration for HTTPS
	protocol = "any", -- Accept any SSL/TLS version
	options = { "all", "no_sslv2", "no_sslv3" }, -- Disable insecure SSL versions
	verify = "none", -- Skip certificate verification (required for Kindles with outdated cert stores)
	}

	-- Choose HTTP or HTTPS based on URL scheme
	local httpx = request_url:match("^https://") and https or http
	local success_code, status_code = httpx.request(request)

	logger.dbg("TRMNL: Success code:", success_code)
	logger.dbg("TRMNL: HTTP status code:", status_code)

	if not success_code or success_code ~= 1 then
	logger.err("TRMNL: Request failed - success code:", success_code)
	local context = "Network error - check WiFi connection\nURL: " .. request_url
	self:showError(T(_("Failed to reach TRMNL API (code: %1)"), tostring(success_code)), context)
	return nil
	end

	if status_code ~= 200 then
	logger.err("TRMNL: API returned HTTP", status_code)
	local context_msg
	if status_code == 401 or status_code == 403 then
	context_msg = "Check your API key in settings"
	elseif status_code == 404 then
	context_msg = "Endpoint not found - verify base URL"
	elseif status_code >= 500 then
	context_msg = "Server error - try again later"
	else
	context_msg = "HTTP " .. tostring(status_code)
	end
	self:showError("API request failed", context_msg)
	return nil
	end

	local response_body = table.concat(sink)
	logger.dbg("TRMNL: Received response:", response_body:sub(1, 200))

	local ok, response = pcall(JSON.decode, response_body)
	if not ok or not response then
	logger.err("TRMNL: Failed to parse JSON response")
	return nil
	end

	return response
	end

	function TrmnlDisplay:downloadImage(image_url, filepath)
	local http = require("socket.http")
	local https = require("ssl.https")
	local ltn12 = require("ltn12")

	logger.info("TRMNL: Downloading image from", image_url)

	local file = io.open(filepath, "wb")
	if not file then
	logger.err("TRMNL: Failed to open file for writing:", filepath)
	return false
	end

	local request = {
	url = image_url,
	sink = ltn12.sink.file(file),
	headers = {
	["User-Agent"] = self.settings.user_agent,
	},
	-- SSL/TLS configuration (same as API request)
	protocol = "any",
	options = { "all", "no_sslv2", "no_sslv3" },
	verify = "none", -- Skip certificate verification (required for Kindles)
	}

	local httpx = image_url:match("^https://") and https or http
	local success_code, status_code = httpx.request(request)

	logger.dbg("TRMNL: Image download success code:", success_code)
	logger.dbg("TRMNL: Image download HTTP status:", status_code)

	if not success_code or success_code ~= 1 then
	logger.err("TRMNL: Image download failed - success code:", success_code)
	os.remove(filepath)
	return false
	end

	if status_code ~= 200 then
	logger.err("TRMNL: Image download failed - HTTP", status_code)
	os.remove(filepath)
	return false
	end

	logger.info("TRMNL: Image downloaded successfully")
	return true
	end

Failed to fetch screen metadata error when using BYOS #7

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