You may find the asynchronous http-client, i.e. cpprestsdk, does not support posting a multipart/form-data request. This MultipartEncoder is a work around to generate the body content of multipart/form-data format. So that then you can use a cpp HTTP-client, which is not limited to cpprestsdk, to post a multipart/form-data request by setting the encoded body content.

1. Clone the MultipartEncoder repository

   # Make sure to clone with --recursive
   git clone --recursive https://github.com/AndsonYe/MultipartEncoder.git

2. If not cloned with --recursive, you need to manually get the cpprestsdk submodle

   Ignore this step if you followed step 1 above.

   git submodule update --init --recursive

3. Install dependencies required by cpprestsdk

   sudo apt-get install g++ git make zlib1g-dev libboost-all-dev libssl-dev cmake

4. Build cpprestsdk. Suppose the directory you cloned MultipartEncoder into is MultipartEncoder_ROOT

   cd $MultipartEncoder_ROOT/cpprestsdk/Release
   mkdir build
   cd build
   cmake ..
   make -j$(nproc)

5. Build MultipartEncoder sample

   cd $MultipartEncoder_ROOT
   make

6. Run the sample

   ./run.sh

   The response is writtern in file $MultipartEncoder/results

MultipartParser parser;                             //Create parser instance;
parser.AddParameter(key, value);                    //Add text parameters using AddParameter
parser.AddFile(key, file_path);                     //Add file content using AddFile
std::string boundary = parser.boundary();           //Get the boundary generated by parser, each parser has its unique boundary, this boundary should be set in the HTTP request's header
std::string body = parser.GenBodyContent();         //Get the encoded multipart/form-data body content

Then you can use boundary and body in any HTTP clients.

Check the parser_test.cpp for complete example.