diff --git a/examples/iec61850_client_example_files/client_example_files.c b/examples/iec61850_client_example_files/client_example_files.c
index 0b3f5f3..33c6750 100644
--- a/examples/iec61850_client_example_files/client_example_files.c
+++ b/examples/iec61850_client_example_files/client_example_files.c
@@ -29,10 +29,10 @@ downloadHandler(void* parameter, uint8_t* buffer, uint32_t bytesRead)
 
     if (bufferPosition + bytesRead < MAX_BUFFER_SIZE) {
         memcpy(downloadBuffer + bufferPosition, buffer, bytesRead);
-        return false;
+        return true;
     }
     else
-        return true;
+        return false;
 }
 
 int main(int argc, char** argv) {
diff --git a/src/hal/socket/win32/socket_win32.c b/src/hal/socket/win32/socket_win32.c
index 1d888e9..528237a 100644
--- a/src/hal/socket/win32/socket_win32.c
+++ b/src/hal/socket/win32/socket_win32.c
@@ -381,7 +381,18 @@ Socket_read(Socket self, uint8_t* buf, int size)
 int
 Socket_write(Socket self, uint8_t* buf, int size)
 {
-	return send(self->fd, (char*) buf, size, 0);
+    int bytes_sent = send(self->fd, (char*) buf, size, 0);
+
+    if (bytes_sent == SOCKET_ERROR) {
+        int errorCode = WSAGetLastError();
+
+        if (errorCode == WSAEWOULDBLOCK)
+            bytes_sent = 0;
+        else
+            bytes_sent = -1;
+    }
+
+	return bytes_sent;
 }
 
 void
diff --git a/src/mms/iso_cotp/cotp.c b/src/mms/iso_cotp/cotp.c
index 83089f0..daa8890 100644
--- a/src/mms/iso_cotp/cotp.c
+++ b/src/mms/iso_cotp/cotp.c
@@ -167,17 +167,29 @@ sendBuffer(CotpConnection* self)
 
     bool retVal = false;
 
-    if (Socket_write(self->socket, ByteBuffer_getBuffer(self->writeBuffer), writeBufferPosition) == writeBufferPosition)
-        retVal = true;
+    int sentBytes;
+
+    do {
+        sentBytes = Socket_write(self->socket, ByteBuffer_getBuffer(self->writeBuffer), writeBufferPosition);
+
+        if (sentBytes == -1)
+            goto exit_function;
+
+    } while (sentBytes == 0);
+
+    retVal = true;
 
     ByteBuffer_setSize(self->writeBuffer, 0);
 
+exit_function:
     return retVal;
 }
 
 CotpIndication
 CotpConnection_sendDataMessage(CotpConnection* self, BufferChain payload)
 {
+    CotpIndication retValue = COTP_OK;
+
     int fragments = 1;
 
     int fragmentPayloadSize = CotpConnection_getTpduSize(self) - COTP_DATA_HEADER_SIZE;
@@ -227,9 +239,6 @@ CotpConnection_sendDataMessage(CotpConnection* self, BufferChain payload)
                 currentChainIndex = 0;
             }
 
-            if (DEBUG_COTP)
-                printf("%02x ", currentChain->buffer[currentChainIndex]);
-
             buffer[bufPos++] = currentChain->buffer[currentChainIndex];
 
             currentChainIndex++;
@@ -242,13 +251,25 @@ CotpConnection_sendDataMessage(CotpConnection* self, BufferChain payload)
         if (DEBUG_COTP)
             printf("COTP: Send COTP fragment %i bufpos: %i\n", fragments, currentBufPos);
 
-        if (!sendBuffer(self))
-            return COTP_ERROR;
+        if (!sendBuffer(self)) {
+            retValue = COTP_ERROR;
+
+            if (DEBUG_COTP)
+                printf("COTP: sending message failed!\n");
+
+            goto exit_function;
+        }
+
 
         fragments--;
     }
 
-    return COTP_OK;
+exit_function:
+
+    if (DEBUG_COTP)
+        printf("COTP: message transmission finished (fragments=%i, return=%i)\n", fragments, retValue);
+
+    return retValue;
 }
 
 static void
@@ -435,16 +456,6 @@ CotpConnection_init(CotpConnection* self, Socket socket,
     self->packetSize = 0;
 }
 
-//void
-//CotpConnection_destroy(CotpConnection* self)
-//{
-//    if (self->writeBuffer != NULL)
-//        ByteBuffer_destroy(self->writeBuffer);
-//
-//    if (self->readBuffer != NULL)
-//        ByteBuffer_destroy(self->readBuffer);
-//}
-
 int /* in byte */
 CotpConnection_getTpduSize(CotpConnection* self)
 {