diff --git a/sys/apis/fs/redfs.lua b/sys/apis/fs/redfs.lua
new file mode 100644
index 0000000..66c97f7
--- /dev/null
+++ b/sys/apis/fs/redfs.lua
@@ -0,0 +1,57 @@
+--[[
+	Mount a readonly file system from another computer across rednet. The
+	target computer must be running OpusOS or redserver.
+
+	Syntax:
+	rn://<id>/directory/subdir
+
+	Examples:
+	rn://12/usr/etc
+	rn://8/usr
+]]--
+
+local rttp = require('rttp')
+
+local fs     = _G.fs
+
+local redfs = { }
+
+local function getListing(uri)
+	local success, response = rttp.get(uri .. '?recursive=true')
+
+	if not success then
+		error(response)
+	end
+
+	if response.statusCode ~= 200 then
+		error('Received response ' .. response.statusCode)
+	end
+
+	local list = { }
+	for _,v in pairs(response.data) do
+		if not v.isDir then
+			list[v.path] = {
+				url = uri .. '/' .. v.path,
+				size = v.size,
+			}
+		end
+	end
+
+	return list
+end
+
+function redfs.mount(dir, uri)
+	if not uri then
+		error('redfs syntax: uri')
+	end
+
+	local list = getListing(uri)
+	for path, entry in pairs(list) do
+		if not fs.exists(fs.combine(dir, path)) then
+			local node = fs.mount(fs.combine(dir, path), 'urlfs', entry.url)
+			node.size = entry.size
+		end
+	end
+end
+
+return redfs
diff --git a/sys/apis/fs/urlfs.lua b/sys/apis/fs/urlfs.lua
index 1c3c60d..c0305b4 100644
--- a/sys/apis/fs/urlfs.lua
+++ b/sys/apis/fs/urlfs.lua
@@ -1,3 +1,4 @@
+local rttp = require('rttp')
 local Util = require('util')
 
 local fs = _G.fs
@@ -50,7 +51,12 @@ function urlfs.open(node, fn, fl)
 
 	local c = node.cache
 	if not c then
-		c = Util.httpGet(node.url)
+		if node.url:match('^([%w][%w%+%-%.]*)%:') == 'rn' then
+			local s, response = rttp.get(node.url)
+			c = s and response.statusCode == 200 and response.data
+		else
+			c = Util.httpGet(node.url)
+		end
 		if c then
 			node.cache = c
 			node.size = #c
diff --git a/sys/apis/rttp.lua b/sys/apis/rttp.lua
new file mode 100644
index 0000000..8696e9e
--- /dev/null
+++ b/sys/apis/rttp.lua
@@ -0,0 +1,95 @@
+local device = _G.device
+local os     = _G.os
+
+local rttp = { }
+local computerId = os.getComputerID()
+
+local function parse(url, default)
+	-- initialize default parameters
+	local parsed = {}
+	local authority
+
+	for i,v in pairs(default or parsed) do parsed[i] = v end
+	-- remove whitespace
+	-- url = string.gsub(url, "%s", "")
+	-- Decode unreserved characters
+	url = string.gsub(url, "%%(%x%x)", function(hex)
+			local char = string.char(tonumber(hex, 16))
+			if string.match(char, "[a-zA-Z0-9._~-]") then
+				return char
+			end
+			-- Hex encodings that are not unreserved must be preserved.
+			return nil
+		end)
+	-- get fragment
+	url = string.gsub(url, "#(.*)$", function(f)
+		parsed.fragment = f
+		return ""
+	end)
+	-- get scheme. Lower-case according to RFC 3986 section 3.1.
+	url = string.gsub(url, "^(%w[%w.+-]*):",
+	function(s) parsed.scheme = string.lower(s); return "" end)
+	-- get authority
+	url = string.gsub(url, "^//([^/]*)", function(n)
+		authority = n
+		return ""
+	end)
+	-- get query stringing
+	url = string.gsub(url, "%?(.*)", function(q)
+		parsed.query = q
+		return ""
+	end)
+	-- get params
+	url = string.gsub(url, "%;(.*)", function(p)
+		parsed.params = p
+		return ""
+	end)
+
+	-- path is whatever was left
+	parsed.path = url
+
+	-- Represents host:port, port = nil if not used.
+	if authority then
+		authority = string.gsub(authority, ":(%d+)$",
+								function(p) parsed.port = tonumber(p); return "" end)
+		if authority ~= "" then
+			parsed.host = authority
+		end
+	end
+	return parsed
+end
+
+function rttp.get(url)
+	local modem  = device.wireless_modem or error('Modem not found')
+	local parsed = parse(url, { port = 80 })
+
+	parsed.host = tonumber(parsed.host) or error('Invalid url')
+
+	for i = 16384, 32767 do
+		if not modem.isOpen(i) then
+			modem.open(i)
+			local path = parsed.query and parsed.path .. '?' .. parsed.query or parsed.path
+
+			modem.transmit(parsed.port, parsed.host, {
+				method = 'GET',
+				replyAddress = computerId,
+				replyPort = i,
+				path = path,
+			})
+			local timerId = os.startTimer(3)
+			repeat
+				local event, id, dport, dhost, response = os.pullEvent()
+				if event == 'modem_message' and
+					dport == i and
+					dhost == computerId and
+					type(response) == 'table' then
+					modem.close(i)
+					return true, response
+				end
+			until event == 'timer' and id == timerId
+			return false, 'timeout'
+		end
+	end
+end
+
+return rttp
diff --git a/sys/boot/opus.boot b/sys/boot/opus.boot
index ef0e8ed..32c7010 100644
--- a/sys/boot/opus.boot
+++ b/sys/boot/opus.boot
@@ -2,7 +2,7 @@
 local fs     = _G.fs
 local http   = _G.http
 
-_G.OPUS_BRANCH = 'master-1.8'
+_G.OPUS_BRANCH = 'develop-1.8'
 local GIT_REPO = 'kepler155c/opus/' .. _G.OPUS_BRANCH
 local BASE     = 'https://raw.githubusercontent.com/' .. GIT_REPO
 
diff --git a/sys/extensions/2.vfs.lua b/sys/extensions/2.vfs.lua
index 2cf39ab..3558c60 100644
--- a/sys/extensions/2.vfs.lua
+++ b/sys/extensions/2.vfs.lua
@@ -149,6 +149,7 @@ function fs.complete(partial, dir, includeFiles, includeSlash)
 end
 
 function fs.listEx(dir)
+  dir = fs.combine(dir, '')
 	local node = getNode(dir)
 	if node.fs.listEx then
 		return node.fs.listEx(node, dir)
diff --git a/sys/kernel.lua b/sys/kernel.lua
index 7ff088e..2f5b457 100644
--- a/sys/kernel.lua
+++ b/sys/kernel.lua
@@ -252,7 +252,7 @@ local function init(...)
 	local files = fs.list(dir)
 	table.sort(files)
 	for _,file in ipairs(files) do
-		local level = file:match('(%d).%S+.lua')
+		local level = file:match('(%d).%S+.lua') or 99
 		if tonumber(level) <= runLevel then
 			local s, m = shell.run(fs.combine(dir, file))
 			if not s then
diff --git a/sys/network/redserver.lua b/sys/network/redserver.lua
new file mode 100644
index 0000000..f4f9351
--- /dev/null
+++ b/sys/network/redserver.lua
@@ -0,0 +1,109 @@
+local Event = require('event')
+local Util  = require('util')
+
+local fs    = _G.fs
+local modem = _G.device.wireless_modem
+local os    = _G.os
+
+local computerId = os.getComputerID()
+
+modem.open(80)
+
+-- https://github.com/golgote/neturl/blob/master/lib/net/url.lua
+local function parseQuery(str)
+	local sep = '&'
+
+	local values = {}
+	for key,val in str:gmatch(string.format('([^%q=]+)(=*[^%q=]*)', sep, sep)) do
+		--local key = decode(key)
+		local keys = {}
+		key = key:gsub('%[([^%]]*)%]', function(v)
+				-- extract keys between balanced brackets
+				if string.find(v, "^-?%d+$") then
+					v = tonumber(v)
+				--else
+					--v = decode(v)
+				end
+				table.insert(keys, v)
+				return "="
+		end)
+		key = key:gsub('=+.*$', "")
+		key = key:gsub('%s', "_") -- remove spaces in parameter name
+		val = val:gsub('^=+', "")
+
+		if not values[key] then
+			values[key] = {}
+		end
+		if #keys > 0 and type(values[key]) ~= 'table' then
+			values[key] = {}
+		elseif #keys == 0 and type(values[key]) == 'table' then
+			values[key] = val --decode(val)
+		end
+
+		local t = values[key]
+		for i,k in ipairs(keys) do
+			if type(t) ~= 'table' then
+				t = {}
+			end
+			if k == "" then
+				k = #t+1
+			end
+			if not t[k] then
+				t[k] = {}
+			end
+			if i == #keys then
+				t[k] = val --decode(val)
+			end
+			t = t[k]
+		end
+	end
+	return values
+end
+
+local function getListing(path, recursive)
+	local list = { }
+	local function listing(p)
+		for _, f in pairs(fs.listEx(p)) do
+			local abs = fs.combine(p, f.name)
+			table.insert(list, {
+				isDir = f.isDir,
+				path = string.sub(abs, #path + 1),
+				size = f.size,
+			})
+			if recursive and f.isDir then
+				listing(abs)
+			end
+		end
+	end
+	listing(path)
+	return list
+end
+
+Event.on('modem_message', function(_, _, dport, dhost, request)
+	if dport == 80 and dhost == computerId and type(request) == 'table' then
+		if request.method == 'GET' then
+			local query
+			local path = request.path:gsub('%?(.*)', function(v)
+				query = parseQuery(v)
+				return ''
+			end)
+			if fs.isDir(path) then
+				modem.transmit(request.replyPort, request.replyAddress, {
+					statusCode = 200,
+					contentType = 'table/directory',
+					data = getListing(path, query and query.recursive == 'true'),
+				})
+			elseif fs.exists(path) then
+				modem.transmit(request.replyPort, request.replyAddress, {
+					statusCode = 200,
+					contentType = 'table/file',
+					data = Util.readFile(path),
+				})
+			else
+				modem.transmit(request.replyPort, request.replyAddress, {
+					statusCode = 404,
+				})
+			end
+		end
+	end
+end)
diff --git a/sys/network/transport.lua b/sys/network/transport.lua
index 57fe323..77342c2 100644
--- a/sys/network/transport.lua
+++ b/sys/network/transport.lua
@@ -74,7 +74,7 @@ Event.on('timer', function(_, timerId)
 end)
 
 Event.on('modem_message', function(_, _, dport, dhost, msg, distance)
-	if dhost == computerId and msg then
+	if dhost == computerId and type(msg) == 'table' then
 		local socket = transport.sockets[dport]
 		if socket and socket.connected then