Question

There is a server that response a .png file over http:

#include "server.h"
string Server::header(int contentLength)
{
    string h =
    "HTTP/1.1 200 OK\n"
    "Content-Length: " + boost::lexical_cast<string>(contentLength) + "\n"
    "Content-Type: image/png;\n"
    "Connection: close\n"
    "\n";
    return h;
}
string Server::readMap(const string &filename)
{
    ifstream file (filename.c_str(), ios::in|ios::binary);
    string reply;
    char buf[512];
    while (file.read(buf, sizeof(buf)).gcount() > 0)
        reply.append(buf, file.gcount());
    return reply;
}
void Server::run(const string &filename, int port)
{
    string data = readMap(filename);
    try
    {
        boost::asio::io_service io_service;
        tcp::acceptor acceptor(io_service, tcp::endpoint(tcp::v4(), port));
        for (;;)
        {
          tcp::socket socket(io_service);
          acceptor.accept(socket);
          boost::asio::write(socket, boost::asio::buffer(header( data.size() )));
          boost::asio::write(socket, boost::asio::buffer(data));
        }
    }
    catch (std::exception& e)
    {
        cerr << "exception: " << e.what() << endl;
    }
}

Every time an error happens:

exception: Connection reset by peer

I can see some part of an image in my browser, and sometimes the image is almost complete, but it never works without the error.

If I use wget it looks like

wget http://localhost:8089
--2012-03-07 12:07:19--  http://localhost:8089/
Resolving localhost... 127.0.0.1
Connecting to localhost|127.0.0.1|:8089... connected.
HTTP request sent, awaiting response... 200 OK
Length: 760032 (742K) [image/png]
Saving to: `index.html'

62% [========================================================>                                   ] 475,136     --.-K/s   in 0.002s  

2012-03-07 12:07:19 (287 MB/s) - Read error at byte 475136/760032 (Connection reset by peer). Retrying.

--2012-03-07 12:07:20--  (try: 2)  http://localhost:8089/
Connecting to localhost|127.0.0.1|:8089... connected.
HTTP request sent, awaiting response... 200 OK
Length: 760032 (742K) [image/png]
Saving to: `index.html'

73% [==================================================================>                         ] 557,056     --.-K/s   in 0.001s  

... many failes and finally

--2012-03-07 12:09:01--  (try: 9)  http://localhost:8089/
Connecting to localhost|127.0.0.1|:8089... connected.
HTTP request sent, awaiting response... 200 OK
Length: 760032 (742K) [image/png]
Saving to: `index.html'

100%[===========================================================================================>] 760,032     --.-K/s   in 0.001s 

Any ideas how to fix it?

Answer 1

There are several more complete HTTP-implementations in the ASIO-docs, including static file serving. One way to go would be to reuse some of that sample code for your application.

In this particular case, there’s an example of how to correctly open and buffer a file at http://www.boost.org/doc/libs/1_49_0/doc/html/boost_asio/example/http/server/request_handler.cpp

  std::ifstream is(full_path.c_str(), std::ios::in | std::ios::binary);
    ...
  char buf[512];
  while (is.read(buf, sizeof(buf)).gcount() > 0)
    rep.content.append(buf, is.gcount());

The docs also has examples for actual asynchronous HTTP-implementations. (I assume you’re using boost::asio to eventually make it asynchronous?)