diff --git a/include/freerdp/transport_io.h b/include/freerdp/transport_io.h
index 6a5726ebf..bfa55cb14 100644
--- a/include/freerdp/transport_io.h
+++ b/include/freerdp/transport_io.h
@@ -38,7 +38,10 @@ extern "C"
 	 * @param userContext user defined context passed by @ref freerdp_set_io_callback_context
 	 * @param data a buffer to read to
 	 * @param bytes the size of the buffer
-	 * @return the number of bytes read or <0 for failures
+	 * @return the number of bytes read. Negative numbers indicate an error
+	 * occurred. \b errno is set accordingly (see man 2 read)
+	 * @bug Before 3.18.0 the function did return \b -1 for transport closed and \b 0 for retry
+	 * events.
 	 * @since version 3.9.0
 	 */
 	typedef int (*pTransportLayerRead)(void* userContext, void* data, int bytes);
@@ -48,7 +51,10 @@ extern "C"
 	 * @param userContext user defined context passed by @ref freerdp_set_io_callback_context
 	 * @param data a buffer to write
 	 * @param bytes the size of the buffer
-	 * @return the number of bytes written or <0 for failures
+	 * @return the number of bytes written. Negative numbers indicate an error
+	 * occurred. \b errno is set accordingly (see man 2 send)
+	 * @bug Before 3.18.0 the function did return \b -1 for transport closed and \b 0 for retry
+	 * events.
 	 * @since version 3.9.0
 	 */
 	typedef int (*pTransportLayerWrite)(void* userContext, const void* data, int bytes);
@@ -109,14 +115,14 @@ extern "C"
 		pTransportFkt TLSAccept;
 		pTransportAttach TransportAttach;
 		pTransportFkt TransportDisconnect;
-		pTransportRWFkt ReadPdu;  /* Reads a whole PDU from the transport */
-		pTransportRWFkt WritePdu; /* Writes a whole PDU to the transport */
-		pTransportRead ReadBytes; /* Reads up to a requested amount of bytes */
+		pTransportRWFkt ReadPdu;                   /* Reads a whole PDU from the transport */
+		pTransportRWFkt WritePdu;                  /* Writes a whole PDU to the transport */
+		pTransportRead ReadBytes;                  /* Reads up to a requested amount of bytes */
 		pTransportGetPublicKey GetPublicKey;       /** @since version 3.2.0 */
 		pTransportSetBlockingMode SetBlockingMode; /** @since version 3.3.0 */
 		pTransportConnectLayer ConnectLayer;       /** @since 3.9.0 */
 		pTransportAttachLayer AttachLayer;         /** @since 3.9.0 */
-		UINT64 reserved[64 - 12]; /* Reserve some space for ABI compatibility */
+		UINT64 reserved[64 - 12];                  /* Reserve some space for ABI compatibility */
 	};
 	typedef struct rdp_transport_io rdpTransportIo;
 
diff --git a/libfreerdp/core/proxy.c b/libfreerdp/core/proxy.c
index 03b1aeb08..76e2e2e14 100644
--- a/libfreerdp/core/proxy.c
+++ b/libfreerdp/core/proxy.c
@@ -696,12 +696,6 @@ static BOOL http_proxy_connect(rdpContext* context, BIO* bufferedBio, const char
 			}
 			Sleep(10);
 		}
-		else
-		{
-			/* Error? */
-			WLog_ERR(TAG, "Failed reading reply from HTTP proxy (BIO_read returned zero)");
-			goto fail;
-		}
 
 		resultsize += WINPR_ASSERTING_INT_CAST(size_t, status);
 	}
diff --git a/libfreerdp/core/tcp.c b/libfreerdp/core/tcp.c
index 76e95cbf7..456ba84b6 100644
--- a/libfreerdp/core/tcp.c
+++ b/libfreerdp/core/tcp.c
@@ -1354,29 +1354,17 @@ static int freerdp_tcp_layer_read(void* userContext, void* data, int bytes)
 
 	rdpTcpLayer* tcpLayer = (rdpTcpLayer*)userContext;
 
-	int error = 0;
-	int status = 0;
-
 	(void)WSAResetEvent(tcpLayer->hEvent);
-	status = _recv((SOCKET)tcpLayer->sockfd, data, bytes, 0);
+	const int status = _recv((SOCKET)tcpLayer->sockfd, data, bytes, 0);
 
 	if (status > 0)
 		return status;
 
-	if (status == 0)
-		return -1; /* socket closed */
-
-	error = WSAGetLastError();
+	const int error = WSAGetLastError();
 
 	if ((error == WSAEWOULDBLOCK) || (error == WSAEINTR) || (error == WSAEINPROGRESS) ||
 	    (error == WSAEALREADY))
-	{
-		status = 0;
-	}
-	else
-	{
-		status = -1;
-	}
+		errno = EAGAIN;
 
 	return status;
 }
@@ -1390,25 +1378,15 @@ static int freerdp_tcp_layer_write(void* userContext, const void* data, int byte
 
 	rdpTcpLayer* tcpLayer = (rdpTcpLayer*)userContext;
 
-	int error = 0;
-	int status = 0;
+	const int status = _send((SOCKET)tcpLayer->sockfd, data, bytes, 0);
+	if (status > 0)
+		return status;
 
-	status = _send((SOCKET)tcpLayer->sockfd, data, bytes, 0);
+	const int error = WSAGetLastError();
 
-	if (status <= 0)
-	{
-		error = WSAGetLastError();
-
-		if ((error == WSAEWOULDBLOCK) || (error == WSAEINTR) || (error == WSAEINPROGRESS) ||
-		    (error == WSAEALREADY))
-		{
-			status = 0;
-		}
-		else
-		{
-			status = -1;
-		}
-	}
+	if ((error == WSAEWOULDBLOCK) || (error == WSAEINTR) || (error == WSAEINPROGRESS) ||
+	    (error == WSAEALREADY))
+		errno = EAGAIN;
 
 	return status;
 }
diff --git a/libfreerdp/core/transport.c b/libfreerdp/core/transport.c
index 21523f2ae..b06e9f107 100644
--- a/libfreerdp/core/transport.c
+++ b/libfreerdp/core/transport.c
@@ -1961,11 +1961,21 @@ static int transport_layer_bio_write(BIO* bio, const char* buf, int size)
 
 	BIO_clear_flags(bio, BIO_FLAGS_WRITE | BIO_FLAGS_SHOULD_RETRY);
 
-	int status = IFCALLRESULT(-1, layer->Write, layer->userContext, buf, size);
+	errno = 0;
+	const int status = IFCALLRESULT(-1, layer->Write, layer->userContext, buf, size);
 
 	if (status >= 0 && status < size)
 		BIO_set_flags(bio, (BIO_FLAGS_WRITE | BIO_FLAGS_SHOULD_RETRY));
 
+	switch (errno)
+	{
+		case EAGAIN:
+			BIO_set_flags(bio, (BIO_FLAGS_WRITE | BIO_FLAGS_SHOULD_RETRY));
+			break;
+		default:
+			break;
+	}
+
 	return status;
 }
 
@@ -1983,11 +1993,17 @@ static int transport_layer_bio_read(BIO* bio, char* buf, int size)
 		return -1;
 
 	BIO_clear_flags(bio, BIO_FLAGS_READ | BIO_FLAGS_SHOULD_RETRY);
+	errno = 0;
+	const int status = IFCALLRESULT(-1, layer->Read, layer->userContext, buf, size);
 
-	int status = IFCALLRESULT(-1, layer->Read, layer->userContext, buf, size);
-
-	if (status == 0)
-		BIO_set_flags(bio, (BIO_FLAGS_READ | BIO_FLAGS_SHOULD_RETRY));
+	switch (errno)
+	{
+		case EAGAIN:
+			BIO_set_flags(bio, (BIO_FLAGS_READ | BIO_FLAGS_SHOULD_RETRY));
+			break;
+		default:
+			break;
+	}
 
 	return status;
 }