DatagramSocket: Added shutdown method to cleanly exit from Datagram Read/Write loop without destroying the object (useful to resolve race conditions).

modules/juce_core/network/juce_Socket.cpp

@@ -569,8 +569,11 @@ DatagramSocket::DatagramSocket (const bool canBroadcast)
     SocketHelpers::initSockets();
 
     handle = (int) socket (AF_INET, SOCK_DGRAM, 0);
-    SocketHelpers::resetSocketOptions (handle, true, canBroadcast);
-    SocketHelpers::makeReusable (handle);
+    if (handle >= 0)
+    {
+        SocketHelpers::resetSocketOptions (handle, true, canBroadcast);
+        SocketHelpers::makeReusable (handle);
+    }
 }
 
 DatagramSocket::~DatagramSocket()
@@ -578,8 +581,18 @@ DatagramSocket::~DatagramSocket()
     if (lastServerAddress != nullptr)
         freeaddrinfo (static_cast <struct addrinfo*> (lastServerAddress));
 
+    shutdown();
+}
+
+void DatagramSocket::shutdown()
+{
+    if (handle < 0)
+        return;
+
+    int copyOfHandle = handle;
+    handle = -1;
     bool connected = false;
-    SocketHelpers::closeSocket (handle, readLock, false, 0, connected);
+    SocketHelpers::closeSocket (copyOfHandle, readLock, false, 0, connected);
 }
 
 bool DatagramSocket::bindToPort (const int port)
@@ -589,6 +602,9 @@ bool DatagramSocket::bindToPort (const int port)
 
 bool DatagramSocket::bindToPort (const int port, const String& addr)
 {
+    if (handle < 0)
+        return false;
+
     if (SocketHelpers::bindSocket (handle, port, addr))
     {
         isBound = true;
@@ -602,6 +618,9 @@ bool DatagramSocket::bindToPort (const int port, const String& addr)
 
 int DatagramSocket::getBoundPort() const noexcept
 {
+    if (handle < 0)
+        return -1;
+
     return isBound ? SocketHelpers::getBoundPort (handle) : -1;
 }
 
@@ -609,11 +628,17 @@ int DatagramSocket::getBoundPort() const noexcept
 int DatagramSocket::waitUntilReady (const bool readyForReading,
                                     const int timeoutMsecs) const
 {
+    if (handle < 0)
+        return -1;
+
     return SocketHelpers::waitForReadiness (handle, readLock, readyForReading, timeoutMsecs);
 }
 
 int DatagramSocket::read (void* destBuffer, int maxBytesToRead, bool shouldBlock)
 {
+    if (handle < 0)
+        return -1;
+
     bool connected = true;
     return isBound ? SocketHelpers::readSocket (handle, destBuffer, maxBytesToRead,
                                                 connected, shouldBlock, readLock) : -1;
@@ -621,6 +646,9 @@ int DatagramSocket::read (void* destBuffer, int maxBytesToRead, bool shouldBlock
 
 int DatagramSocket::read (void* destBuffer, int maxBytesToRead, bool shouldBlock, String& senderIPAddress, int& senderPort)
 {
+    if (handle < 0)
+        return -1;
+
     bool connected = true;
     return isBound ? SocketHelpers::readSocket (handle, destBuffer, maxBytesToRead, connected,
                                                 shouldBlock, readLock, &senderIPAddress, &senderPort) : -1;
@@ -629,6 +657,9 @@ int DatagramSocket::read (void* destBuffer, int maxBytesToRead, bool shouldBlock
 int DatagramSocket::write (const String& remoteHostname, int remotePortNumber,
                            const void* sourceBuffer, int numBytesToWrite)
 {
+    if (handle < 0)
+        return -1;
+
     struct addrinfo*& info = reinterpret_cast <struct addrinfo*&> (lastServerAddress);
 
     // getaddrinfo can be quite slow so cache the result of the address lookup
@@ -651,7 +682,7 @@ int DatagramSocket::write (const String& remoteHostname, int remotePortNumber,
 
 bool DatagramSocket::joinMulticast (const String& multicastIPAddress)
 {
-    if (! isBound)
+    if (! isBound || handle < 0)
         return false;
 
     return SocketHelpers::multicast (handle, multicastIPAddress, lastBindAddress, true);
@@ -659,7 +690,7 @@ bool DatagramSocket::joinMulticast (const String& multicastIPAddress)
 
 bool DatagramSocket::leaveMulticast (const String& multicastIPAddress)
 {
-    if (! isBound)
+    if (! isBound || handle < 0)
         return false;
 
     return SocketHelpers::multicast (handle, multicastIPAddress, lastBindAddress, false);

modules/juce_core/network/juce_Socket.h

@@ -306,6 +306,20 @@ public:
     int write (const String& remoteHostname, int remotePortNumber,
                const void* sourceBuffer, int numBytesToWrite);
 
+    /** Closes the underlying socket object.
+
+        Closes the underlying socket object and aborts any read or write operations.
+        Note that all other methods will return an error after this call. This
+        method is useful if another thread is blocking in a read/write call and you
+        woould like to abort the read/write thread. Simply deleting the socket
+        object without calling shutdown may cause a race-condition where the read/write
+        returns just before the socket is deleted and the subsequent read/write would
+        try to read from an invalid pointer. By calling shutdown first, the socket
+        object remains valid but all current and subsequent calls to read/write will
+        return immediately.
+    */
+    void shutdown();
+
     //==============================================================================
     /** Join a multicast group