[Boost-users] ASIO UDP Communication stops working when entering a thread

25 Sep 2013

      Have created a class to allow  UDP communication using ASIO

// Header
class    UdpClient
{
     public:
         UdpClient();
         void Open(string ipaddr, string port);
         void Send(string packet);
         void Close();
     private:
         bool        init;
         string        ipAddress;
         string        Port;
         udp::endpoint     Endpoint;
         udp::socket    *pSocket;
         udp::socket    *s;
};

// Part of code
void UdpClient::Open(string ipaddr, string port)
{
     ipAddress    = ipaddr;
     Port        = port;

     boost::asio::io_service io_service;

     udp::resolver         resolver(io_service);
     udp::resolver::query    query(udp::v4(), ipaddr,port);
     Endpoint =         *resolver.resolve(query);

     pSocket = new udp::socket(io_service);
     pSocket->open(udp::v4());
     pSocket->send_to(boost::asio::buffer(first.c_str(), first.size()), 
Endpoint);

     std::cout << "Opening port [" + Port + "] on " + ipAddress + "\n";
     init    = true;
}

void UdpClient::Send(string packet)
{
     if (init) {
         pSocket->send_to(boost::asio::buffer(packet.c_str(), 
packet.size()), Endpoint);
     }
}

---------------
Another class implements more advanced communication.

// Extracts
extern    UdpClient    endpoint;

void UdpDebug::WriteLine(string line)
{
     line = "[" + Clock.Now() + "]" + line;
     endpoint.Send(line);
};

------------------------

In my main program i declare two global variables.

UdpDebug        DebugPort;
UdpClient        endpoint;

The I init the UDP communication by calling

endpoint.Open(IPAddress, UDPPort);

after that I can write to the UDP enpoint by:

DebugPort.WriteLine("Debug working!");

Have declared a thread:

boost::thread t1(Initialize);

void Initialize()
{
         DebugPort.WriteLine("Debug working in the thread");
         for (int i = 0; i < MAX; ++i) {
             wait(1);
             std::cout << "Thread 1: "  << i << std::endl;
        }
}

When I do

t1.join();

The thread starts printing out "Thread1: <number>" on the terminal
but no UDP output is received on the other end.

Any clues why this won't work?

Are starting two threads, but only one of them is attempting UDP 
communication.

If I put a wait statement inside the main program, and attempt UDP 
communication
after the threads have executed a few seconds, this will still work.

Also tried creating a new instance of UdpClient inside the thread.
Opened it, and tried to send data, to no avail.

Any clues?

BR
Ulf Samuelsson