diff --git a/lualib/http/httpc.lua b/lualib/http/httpc.lua
index bc18dad0..54595648 100644
--- a/lualib/http/httpc.lua
+++ b/lualib/http/httpc.lua
@@ -2,8 +2,12 @@ local skynet = require "skynet"
 local socket = require "http.sockethelper"
 local internal = require "http.internal"
 local dns = require "skynet.dns"
+
 local string = string
 local table = table
+local pcall = pcall
+local error = error
+local pairs = pairs
 
 local httpc = {}
 
diff --git a/lualib/http/httpd.lua b/lualib/http/httpd.lua
index 1575f5a6..fb3fb2e8 100644
--- a/lualib/http/httpd.lua
+++ b/lualib/http/httpd.lua
@@ -2,6 +2,11 @@ local internal = require "http.internal"
 
 local string = string
 local type = type
+local assert = assert
+local tonumber = tonumber
+local pcall = pcall
+local ipairs = ipairs
+local pairs = pairs
 
 local httpd = {}
 
diff --git a/lualib/http/internal.lua b/lualib/http/internal.lua
index 204767be..a34b7df6 100644
--- a/lualib/http/internal.lua
+++ b/lualib/http/internal.lua
@@ -1,5 +1,11 @@
 local table = table
 local type = type
+local string = string
+local tonumber = tonumber
+local pcall = pcall
+local assert = assert
+local error = error
+local pairs = pairs
 
 local M = {}
 
diff --git a/lualib/http/sockethelper.lua b/lualib/http/sockethelper.lua
index 10b32346..9f0a6d03 100644
--- a/lualib/http/sockethelper.lua
+++ b/lualib/http/sockethelper.lua
@@ -1,11 +1,26 @@
 local socket = require "skynet.socket"
 local skynet = require "skynet"
 
+local coroutine = coroutine
+local error = error
+local tostring = tostring
+
 local readbytes = socket.read
 local writebytes = socket.write
 
 local sockethelper = {}
-local socket_error = setmetatable({} , { __tostring = function() return "[Socket Error]" end })
+local socket_error = setmetatable({} , { 
+	__tostring = function(self)
+		local info = self.err_info
+		self.err_info = nil
+		return info or "[Socket Error]"
+	end,
+
+	__call = function (self, info)
+		self.err_info = "[Socket Error] : " .. tostring(info)
+		return self
+	end
+})
 
 sockethelper.socket_error = socket_error
 
@@ -27,7 +42,7 @@ local function preread(fd, str)
 					if ret then
 						return str .. ret
 					else
-						error(socket_error)
+						error(socket_error("read failed fd = " .. fd))
 					end
 				end
 			end
@@ -36,7 +51,7 @@ local function preread(fd, str)
 			if ret then
 				return ret
 			else
-				error(socket_error)
+				error(socket_error("read failed fd = " .. fd))
 			end
 		end
 	end
@@ -51,7 +66,7 @@ function sockethelper.readfunc(fd, pre)
 		if ret then
 			return ret
 		else
-			error(socket_error)
+			error(socket_error("read failed fd = " .. fd))
 		end
 	end
 end
@@ -62,24 +77,27 @@ function sockethelper.writefunc(fd)
 	return function(content)
 		local ok = writebytes(fd, content)
 		if not ok then
-			error(socket_error)
+			error(socket_error("write failed fd = " .. fd))
 		end
 	end
 end
 
 function sockethelper.connect(host, port, timeout)
-	local fd
+	local fd, err
+	local is_time_out = false
 	if timeout then
+		is_time_out = true
 		local drop_fd
 		local co = coroutine.running()
 		-- asynchronous connect
 		skynet.fork(function()
-			fd = socket.open(host, port)
+			fd, err = socket.open(host, port)
 			if drop_fd then
 				-- sockethelper.connect already return, and raise socket_error
 				socket.close(fd)
 			else
 				-- socket.open before sleep, wakeup.
+				is_time_out = false
 				skynet.wakeup(co)
 			end
 		end)
@@ -89,13 +107,14 @@ function sockethelper.connect(host, port, timeout)
 			drop_fd = true
 		end
 	else
+		is_time_out = false
 		-- block connect
 		fd = socket.open(host, port)
 	end
 	if fd then
 		return fd
 	end
-	error(socket_error)
+	error(socket_error("connect failed host = " .. host .. ' port = '.. port .. ' timeout = ' .. timeout .. ' err = ' .. tostring(err) .. ' is_time_out = '.. tostring(is_time_out)))
 end
 
 function sockethelper.close(fd)