HOW-TO: Client connection manager for Boost::asio? - c++

Question

I created a server using boost:asio. When a client connects it sends a file_size, file_name and the file_data. The server stores this in a file on disk. This works perfectly! Though now I'm running both client application and server application in the main thread of their application (so I've got a server and client app) which blocks the rest of the application(s) from executing.
So in abstract I want to create something like this:
server app
have one thread to receive and handle all incoming file transfers
have another thread in which the rest of the application can do the things it want to
client app
when I press the space bar, or whenever i want, I want to send a file to the server in a separate thread from the main one so my application can continue doing other stuff it needs to do.
My question: how do I create a manager for my client file transfers?
File transfer server accepts new file transfer client connections
#include "ofxFileTransferServer.h"
ofxFileTransferServer::ofxFileTransferServer(unsigned short nPort)
:acceptor(
io_service
,boost::asio::ip::tcp::endpoint(
boost::asio::ip::tcp::v4()
,nPort
)
,true
)
,port(nPort)
{
}
// test
void ofxFileTransferServer::startThread() {
boost::thread t(boost::bind(
&ofxFileTransferServer::accept
,this
));
}
void ofxFileTransferServer::accept() {
ofxFileTransferConnection::pointer new_connection(new ofxFileTransferConnection(io_service));
acceptor.async_accept(
new_connection->socket()
,boost::bind(
&ofxFileTransferServer::handleAccept
,this
,new_connection
,boost::asio::placeholders::error
)
);
std::cout << __FUNCTION__ << " start accepting " << std::endl;
io_service.run();
}
void ofxFileTransferServer::handleAccept(
ofxFileTransferConnection::pointer pConnection
,const boost::system::error_code& rErr
)
{
std::cout << __FUNCTION__ << " " << rErr << ", " << rErr.message() << std::endl;
if(!rErr) {
pConnection->start();
ofxFileTransferConnection::pointer new_connection(new ofxFileTransferConnection(io_service));
acceptor.async_accept(
new_connection->socket()
,boost::bind(
&ofxFileTransferServer::handleAccept
,this
,new_connection
,boost::asio::placeholders::error
)
);
}
}
File transfer client
#include "ofxFileTransferClient.h"
#include "ofMain.h"
using boost::asio::ip::tcp;
ofxFileTransferClient::ofxFileTransferClient(
boost::asio::io_service &rIOService
,const std::string sServer
,const std::string nPort
,const std::string sFilePath
):resolver_(rIOService)
,socket_(rIOService)
,file_path_(sFilePath)
,server_(sServer)
,port_(nPort)
{
}
ofxFileTransferClient::~ofxFileTransferClient() {
std::cout << "~~~~ ofxFileTransferClient" << std::endl;
}
void ofxFileTransferClient::start() {
// open file / get size
source_file_stream_.open(
ofToDataPath(file_path_).c_str()
,std::ios_base::binary | std::ios_base::ate
);
if(!source_file_stream_) {
std::cout << ">> failed to open:" << file_path_ << std::endl;
return;
}
size_t file_size = source_file_stream_.tellg();
source_file_stream_.seekg(0);
// send file size and name to server.
std::ostream request_stream(&request_);
request_stream << file_path_ << "\n"
<< file_size << "\n\n";
std::cout << ">> request_size:" << request_.size()
<< " file_path: " << file_path_
<< " file_size: "<< file_size
<< std::endl;
// resolve ofxFileTransferServer
tcp::resolver::query query(server_, port_);
resolver_.async_resolve(
query
,boost::bind(
&ofxFileTransferClient::handleResolve
,shared_from_this()
,boost::asio::placeholders::error
,boost::asio::placeholders::iterator
)
);
}
void ofxFileTransferClient::handleResolve(
const boost::system::error_code& rErr
,tcp::resolver::iterator oEndPointIt
)
{
if(!rErr) {
tcp::endpoint endpoint = *oEndPointIt;
socket_.async_connect(
endpoint
,boost::bind(
&ofxFileTransferClient::handleConnect
,shared_from_this()
,boost::asio::placeholders::error
,++oEndPointIt
)
);
}
else {
std::cout << ">> error: " << rErr.message() << std::endl;
}
}
void ofxFileTransferClient::handleConnect(
const boost::system::error_code& rErr
,tcp::resolver::iterator oEndPointIt
)
{
if(!rErr) {
cout << ">> connected!" << std::endl;
boost::asio::async_write(
socket_
,request_
,boost::bind(
&ofxFileTransferClient::handleFileWrite
,shared_from_this()
,boost::asio::placeholders::error
)
);
}
else if (oEndPointIt != tcp::resolver::iterator()) {
// connection failed, try next endpoint in list
socket_.close();
tcp::endpoint endpoint = *oEndPointIt;
socket_.async_connect(
endpoint
,boost::bind(
&ofxFileTransferClient::handleConnect
,shared_from_this()
,boost::asio::placeholders::error
,++oEndPointIt
)
);
}
else {
std::cout << ">> error: " << rErr.message() << std::endl;
}
}
void ofxFileTransferClient::handleFileWrite(
const boost::system::error_code& rErr
)
{
if(!rErr) {
if(source_file_stream_.eof() == false) {
source_file_stream_.read(buf_.c_array(), buf_.size());
if(source_file_stream_.gcount() <= 0) {
std::cout << ">> read file error." << std::endl;
return;
}
std::cout << ">> send: " << source_file_stream_.gcount() << " bytes, total: " << source_file_stream_.tellg() << " bytes\n";
boost::asio::async_write(
socket_
,boost::asio::buffer(buf_.c_array(), source_file_stream_.gcount())
,boost::bind(
&ofxFileTransferClient::handleFileWrite
,this
,boost::asio::placeholders::error
)
);
if(rErr) {
std::cout <<">> send error: " << rErr << std::endl; // not sure bout this one..
}
}
else {
return; // eof()
}
}
else {
std::cout << ">> error:" << rErr.message() << std::endl;
}
}
And a tiny manager to manager client transfers (which is used in the client app)
Again the threading code is only for testing purposes and isnt used.
#include "ofxFileTransferManager.h"
ofxFileTransferManager::ofxFileTransferManager() {
}
void ofxFileTransferManager::transferFile(
const std::string sServer
,const std::string nPort
,const std::string sFile
)
{
ofxFileTransferClient::pointer client(new ofxFileTransferClient(
io_service_
,sServer
,nPort
,sFile
));
client->start();
io_service_.run();
}
void ofxFileTransferManager::startThread() {
boost::thread t(boost::bind(
&ofxFileTransferManager::run
,this
));
}
void ofxFileTransferManager::run() {
cout << "starting filemanager" << std::endl;
while(true) {
io_service_.run();
boost::this_thread::sleep(boost::posix_time::milliseconds(250));
cout << ".";
}
cout << "ready filemanager" << std::endl;
}
It would be awesome if someone can help me out here. The example of boost all use a "one-time" client connection which doesn't really help me further.
roxlu

Answer 1

Great! I just figured it out. I had to wrap my io_service around a boost::asio::io_service::work object! (and forgot a shared_from_this()) somewhere. I've uploaded my code here: http://github.com/roxlu/ofxFileTransfer
For convenience here is the manager code:
#include "ofxFileTransferManager.h"
ofxFileTransferManager::ofxFileTransferManager()
:work_(io_service_)
{
}
void ofxFileTransferManager::transferFile(
const std::string sServer
,const std::string nPort
,const std::string sFile
,const std::string sRemoteFile
)
{
ofxFileTransferClient::pointer client(new ofxFileTransferClient(
io_service_
,sServer
,nPort
,sFile
,sRemoteFile
));
client->start();
}
void ofxFileTransferManager::startThread() {
boost::thread t(boost::bind(
&ofxFileTransferManager::run
,this
));
}
void ofxFileTransferManager::run() {
io_service_.run();
}

Answer 2

From what I can tell, all you really need is to create a new thread and put in its main loop io_service.run();.
Obviously, you would have to take care of protecting classes and variables in mutexes that are shared between the appss main thread and asio's thread.
Edit: Something like this?
static sem_t __semSendFile;
static void* asioThread(void*)
{
while( true )
{
sem_wait( &__semSendFile );
io_service.run();
}
return NULL;
}
void ofxFileTransferManager::transferFile(
const std::string sServer
,const std::string nPort
,const std::string sFile
)
{
ofxFileTransferClient::pointer client(new ofxFileTransferClient(
io_service_
,sServer
,nPort
,sFile
));
client->start();
sem_post( &__semSendFile );
}
int main(int argc, char **argv)
{
if ( sem_init( &__semSendFile, 0, 0 ) != 0 )
{
std::cerr << strerror( errno ) << std::endl;
return -1;
}
pthread_t thread;
if ( pthread_create( &thread, NULL, asioThread, NULL ) != 0 )
{
std::cerr << strerror( errno ) << std::endl;
return -1;
}
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