Fix bugs. Ok, so it didn't work before now.

lib/composite_io.rb

@@ -54,5 +54,6 @@ def local_path
         "#{local_path}"
       end
     EOS
+    io
   end
 end

lib/net/http/post/multipart.rb

@@ -18,8 +18,8 @@ def length
 
         def build_part(boundary, name, value)
           part = ''
-          part << "#{boundary}\r\n"
-          part << "Content-Disposition: form-data; name=\"#{CGI::escape name.to_s}\"\r\n"
+          part << "--#{boundary}\r\n"
+          part << "Content-Disposition: form-data; name=\"#{name.to_s}\"\r\n"
           part << "\r\n"
           part << "#{value}\r\n"
         end
@@ -47,8 +47,8 @@ def length
 
         def build_head(boundary, name, filename, type)
           part = ''
-          part << "#{boundary}\r\n"
-          part << "Content-Disposition: form-data; name=\"#{CGI::escape name.to_s}\"; filename=\"#{filename}\"\r\n"
+          part << "--#{boundary}\r\n"
+          part << "Content-Disposition: form-data; name=\"#{name.to_s}\"; filename=\"#{filename}\"\r\n"
           part << "Content-Type: #{type}\r\n"
           part << "Content-Transfer-Encoding: binary\r\n"
           part << "\r\n"
@@ -59,6 +59,19 @@ def to_io
         end
       end
 
+      class ClosingBoundary
+        def initialize(boundary)
+          @part = "--#{boundary}--\r\n"
+          @io = StringIO.new(@part)
+        end
+        def length
+          @part.length
+        end
+        def to_io
+          @io
+        end
+      end
+
       class Part
         def self.new(boundary, name, value)
           if value.respond_to? :content_type
@@ -75,6 +88,7 @@ class Multipart < Post
         def initialize(path, params, boundary = DEFAULT_BOUNDARY)
           super(path)
           parts = params.map {|k,v| Part.new(boundary, k, v)}
+          parts << ClosingBoundary.new(boundary)
           ios = parts.map{|p| p.to_io }
           self.set_content_type("multipart/form-data", { "boundary" => boundary })
           self.content_length = parts.inject(0) {|sum,i| sum + i.length }