diff --git a/doc/smtp.html b/doc/smtp.html
index b975045..4a9aaac 100644
--- a/doc/smtp.html
+++ b/doc/smtp.html
@@ -122,7 +122,7 @@ smtp.<b>send{</b><br>
 &nbsp;&nbsp;[user = <i>string</i>,]<br>
 &nbsp;&nbsp;[password = <i>string</i>,]<br>
 &nbsp;&nbsp;[server = <i>string</i>,]<br>
-&nbsp;&nbsp;[port = <i>string</i>,]<br>
+&nbsp;&nbsp;[port = <i>number</i>,]<br>
 &nbsp;&nbsp;[domain = <i>string</i>,]<br>
 &nbsp;&nbsp;[step = <i>LTN12 pump step</i>,]<br>
 <b>}</b>
diff --git a/src/ltn12.lua b/src/ltn12.lua
index 9917ce8..ed39ec8 100644
--- a/src/ltn12.lua
+++ b/src/ltn12.lua
@@ -31,6 +31,7 @@ function filter.cycle(low, ctx, extra)
     end
 end
 
+--[[
 local function chain2(f1, f2)
     local ff1, ff2 = "", ""
     return function(chunk)
@@ -55,6 +56,29 @@ local function chain2(f1, f2)
         end
     end
 end
+]]
+
+local function chain2(f1, f2)
+    local co = coroutine.create(function(chunk)
+        while true do
+            local filtered1 = f1(chunk)
+            local filtered2 = f2(filtered1)
+            local done2 = filtered1 and ""
+            while true do
+                if filtered2 == "" or filtered2 == nil then break end
+                coroutine.yield(filtered2)
+                filtered2 = f2(done2)
+            end
+            if filtered1 == "" then chunk = coroutine.yield(filtered1)
+            elseif filtered1 == nil then return nil
+            else chunk = chunk and "" end
+        end
+    end)
+    return function(chunk)
+        local _, res = coroutine.resume(co, chunk)
+        return res
+    end
+end
 
 -- chains a bunch of filters together 
 function filter.chain(...)
diff --git a/test/mimetest.lua b/test/mimetest.lua
index 89926d8..834d99f 100644
--- a/test/mimetest.lua
+++ b/test/mimetest.lua
@@ -187,7 +187,7 @@ local function cleanup_qptest()
 end
 
 -- create test file 
-function create_b64test()
+local function create_b64test()
     local f = assert(io.open(b64test, "wb"))
     local t = {}
     for j = 1, 100 do
@@ -282,8 +282,8 @@ end
 
 local t = socket.gettime()
 
-identity_test()
 create_b64test()
+identity_test()
 encode_b64test()
 decode_b64test()
 compare_b64test()