This code will create a request, and allow to reuse the same connexion for sending more data.

Pipe requests

let pipe_request
    ?socket
    ?headers ?(https=false) ?port ~content ?content_length
    ~http_method ~host ~inet_addr ~uri () =

  let port = match port with
    | None -> if https then 443 else 80
    | Some p -> p
  in
  let sockaddr = Unix.ADDR_INET (inet_addr, port) in
  let fd = (
    match socket with
    | None -> (
      let s = Lwt_unix.socket (Unix.domain_of_sockaddr sockaddr) Unix.SOCK_STREAM 0 in
      Lwt_unix.set_close_on_exec s;
      s)
    | Some x -> x
  ) in

  let initialize_conn () =
    (if https then
              let s = Lwt_ssl.embed_uninitialized_socket fd !sslcontext in
              Ssl.set_client_SNI_hostname
                (Lwt_ssl.ssl_socket_of_uninitialized_socket s) host;
              Lwt_ssl.ssl_perform_handshake s
            else
              Lwt.return (Lwt_ssl.plain fd))
  in

  Lwt.catch
    (fun () ->
       match socket with
      | None -> Lwt_unix.connect fd sockaddr >>= initialize_conn
      | Some x -> initialize_conn ()
    )
    (handle_connection_error fd)
  >>= fun socket ->

  let query = Ocsigen_http_frame.Http_header.Query (http_method, uri) in
  let conn = Ocsigen_http_com.create_receiver
      (Ocsigen_config.get_server_timeout ())
      Ocsigen_http_com.Answer socket in
  let headers =
    Http_headers.replace
      (Http_headers.name "host")
      host
      (match headers with
       | None -> Http_headers.empty
       | Some h -> h)
  in
  let f slot =

    match content with
    | None ->
      let empty_result = Ocsigen_http_frame.Result.empty () in
      Ocsigen_http_com.send
        slot
        ~mode:query
        ~clientproto:Ocsigen_http_frame.Http_header.HTTP11
        ~head:false
        ~keep_alive:false
        ~sender:request_sender
        (Ocsigen_http_frame.Result.update empty_result
           ~headers ())
    | Some stream ->
      Ocsigen_senders.Stream_content.result_of_content stream >>= fun r ->
      Ocsigen_http_com.send
        slot
        ~mode:query
        ~clientproto:Ocsigen_http_frame.Http_header.HTTP11
        ~head:false
        ~keep_alive:false
        ~sender:request_sender
        (Ocsigen_http_frame.Result.update r
           ~content_length
           ~headers ())
  in
  Ocsigen_http_com.start_processing conn f; (* starting the request *)
  (*      Ocsigen_http_com.wait_all_senders conn >>= fun () -> (* not needed *) *)
  Lwt.catch
    (fun () ->
       Ocsigen_http_com.get_http_frame
         ~head:(http_method = Ocsigen_http_frame.Http_header.HEAD)
         conn
       >>= fun http_frame ->
       (match http_frame.Ocsigen_http_frame.frame_content with
        | None   -> Lwt_ssl.close socket
        | Some c ->
          Ocsigen_stream.add_finalizer c (fun _ -> Lwt_ssl.close socket);
          Lwt.return ())
       >>= fun () -> Lwt.return (fd, http_frame))
    (fun e -> Lwt_ssl.close socket >>= fun () -> Lwt.fail e)