Added asynchronous udp receive function (#193)

* Added asynchronous udp receive function

* Remove receive_async and added low level recv, which is non-blocking.

* Remove thread include

* Moved unix include to IXNetSystem.h

ixwebsocket/IXNetSystem.h

@@ -29,6 +29,7 @@ typedef unsigned long int nfds_t;
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <unistd.h>
+#include <fcntl.h>
 #endif
 
 namespace ix

ixwebsocket/IXUdpSocket.cpp

@@ -44,6 +44,18 @@ namespace ix
         return err;
     }
 
+    bool UdpSocket::isWaitNeeded()
+    {
+        int err = getErrno();
+
+        if (err == EWOULDBLOCK || err == EAGAIN || err == EINPROGRESS)
+        {
+            return true;
+        }
+
+        return false;
+    }
+
     void UdpSocket::closeSocket(int fd)
     {
 #ifdef _WIN32
@@ -62,6 +74,13 @@ namespace ix
             return false;
         }
 
+#ifdef _WIN32
+        unsigned long nonblocking = 1;
+        ioctlsocket(sockfd, FIONBIO, &nonblocking);
+#else
+        fcntl(_sockfd, F_SETFL, O_NONBLOCK); // make socket non blocking
+#endif
+
         memset(&_server, 0, sizeof(_server));
         _server.sin_family = AF_INET;
         _server.sin_port = htons(port);
@@ -93,4 +112,11 @@ namespace ix
         return (ssize_t)::sendto(
             _sockfd, buffer.data(), buffer.size(), 0, (struct sockaddr*) &_server, sizeof(_server));
     }
+
+    ssize_t UdpSocket::recvfrom(void* buffer, size_t length)
+    {
+        uint32_t add_len = sizeof(_server);
+        return (ssize_t)::recvfrom(
+            _sockfd, buffer, length, 0, (struct sockaddr*) &_server, &add_len);
+    }
 } // namespace ix

ixwebsocket/IXUdpSocket.h

@@ -18,7 +18,7 @@ typedef SSIZE_T ssize_t;
 #include "IXNetSystem.h"
 
 namespace ix
-{
+{    
     class UdpSocket
     {
     public:
@@ -28,9 +28,12 @@ namespace ix
         // Virtual methods
         bool init(const std::string& host, int port, std::string& errMsg);
         ssize_t sendto(const std::string& buffer);
+        ssize_t recvfrom(void* buffer, size_t length);
+
         void close();
 
         static int getErrno();
+        static bool isWaitNeeded();
         static void closeSocket(int fd);
 
     private: