diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3cc5cfa391..d8ef0cb406 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -249,6 +249,7 @@ option(POCO_ENABLE_STD_MUTEX "Set to OFF|NO using mutex from standard library (d
 if (POCO_ENABLE_STD_MUTEX)
 	add_definitions(-DPOCO_ENABLE_STD_MUTEX)
 endif ()
+
 include(DefinePlatformSpecifc)
 
 # Collect the built libraries and include dirs, the will be used to create the PocoConfig.cmake file
diff --git a/Foundation/include/Poco/Config.h b/Foundation/include/Poco/Config.h
index a0168008a3..bd57425dfc 100644
--- a/Foundation/include/Poco/Config.h
+++ b/Foundation/include/Poco/Config.h
@@ -181,6 +181,10 @@
 //	#define POCO_ENABLE_STD_MUTEX
 #endif
 
+#ifndef POCO_HAVE_SENDFILE
+//	#define POCO_HAVE_SENDFILE
+#endif
+
 #define POCO_HAVE_CPP17_COMPILER (__cplusplus >= 201703L)
 
 // Option to silence deprecation warnings.
diff --git a/Foundation/include/Poco/FileStream.h b/Foundation/include/Poco/FileStream.h
index 662d63e28e..7acd1e2227 100644
--- a/Foundation/include/Poco/FileStream.h
+++ b/Foundation/include/Poco/FileStream.h
@@ -79,7 +79,7 @@ class Foundation_API FileIOS: public virtual std::ios
 	NativeHandle nativeHandle() const;
 		/// Returns native file descriptor handle
 
-	Poco::UInt64 size() const;
+	UInt64 size() const;
 		/// Returns file size
 
 	void flushToDisk();
diff --git a/Foundation/include/Poco/FileStream_POSIX.h b/Foundation/include/Poco/FileStream_POSIX.h
index 0c35b0a07d..a31aa8cd34 100644
--- a/Foundation/include/Poco/FileStream_POSIX.h
+++ b/Foundation/include/Poco/FileStream_POSIX.h
@@ -61,7 +61,7 @@ class Foundation_API FileStreamBuf: public BufferedBidirectionalStreamBuf
 	NativeHandle nativeHandle() const;
 		/// Returns native file descriptor handle
 	
-	Poco::UInt64 size() const;
+	UInt64 size() const;
 		/// Returns file size
 
 protected:
diff --git a/Foundation/include/Poco/Types.h b/Foundation/include/Poco/Types.h
index ed1a386228..965c4553dc 100644
--- a/Foundation/include/Poco/Types.h
+++ b/Foundation/include/Poco/Types.h
@@ -47,7 +47,6 @@ using UInt64  = std::uint64_t;
 using IntPtr  = std::intptr_t;
 using UIntPtr = std::uintptr_t;
 
-
 #if defined(_MSC_VER)
 	#if defined(_WIN64)
 		#define POCO_PTR_IS_64_BIT 1
diff --git a/Net/CMakeLists.txt b/Net/CMakeLists.txt
index 229cdc991b..034f02502d 100644
--- a/Net/CMakeLists.txt
+++ b/Net/CMakeLists.txt
@@ -10,6 +10,28 @@ POCO_HEADERS_AUTO(SRCS ${HDRS_G})
 POCO_SOURCES_AUTO_PLAT(SRCS WIN32 src/wepoll.c)
 POCO_HEADERS_AUTO(SRCS src/wepoll.h)
 
+if (MSVC)
+	set(HAVE_SENDFILE ON)
+else()
+	include(CheckIncludeFiles)
+	include(CheckSymbolExists)
+	check_include_files(sys/sendfile.h HAVE_SYS_SENDFILE_H)
+	if(HAVE_SYS_SENDFILE_H)
+		check_symbol_exists(sendfile sys/sendfile.h HAVE_SENDFILE)
+		if (NOT DEFINED HAVE_SENDFILE)
+			check_symbol_exists(sendfile64 sys/sendfile.h HAVE_SENDFILE)
+		endif()
+	else()
+		# BSD version
+		check_symbol_exists(sendfile "sys/types.h;sys/socket.h;sys/uio.h" HAVE_SENDFILE)
+	endif()
+endif()
+
+if (DEFINED HAVE_SENDFILE)
+	message(STATUS "OS has native sendfile function")
+	add_definitions(-DPOCO_HAVE_SENDFILE)
+endif()
+
 # Version Resource
 if(MSVC AND BUILD_SHARED_LIBS)
 	source_group("Resources" FILES ${PROJECT_SOURCE_DIR}/DLLVersion.rc)
diff --git a/Net/include/Poco/Net/SocketImpl.h b/Net/include/Poco/Net/SocketImpl.h
index 501488e052..2a71877e16 100644
--- a/Net/include/Poco/Net/SocketImpl.h
+++ b/Net/include/Poco/Net/SocketImpl.h
@@ -477,12 +477,17 @@ class Net_API SocketImpl: public Poco::RefCountedObject
 
 	bool initialized() const;
 		/// Returns true iff the underlying socket is initialized.
-
-	Poco::Int64 sendFile(FileInputStream &FileInputStream, Poco::UInt64 offset = 0);
+#ifdef POCO_HAVE_SENDFILE
+	Int64 sendFile(FileInputStream &FileInputStream, UInt64 offset = 0);
 		/// Sends file using system function
 		/// for posix systems - with sendfile[64](...)
 		/// for windows - with TransmitFile(...)
-
+		///
+		/// Returns the number of bytes sent, which may be
+		/// less than the number of bytes specified.
+		///
+		/// Throws NetException (or a subclass) in case of any errors.
+#endif
 protected:
 	SocketImpl();
 		/// Creates a SocketImpl.
diff --git a/Net/include/Poco/Net/StreamSocket.h b/Net/include/Poco/Net/StreamSocket.h
index a71b87acd5..0b219a0310 100644
--- a/Net/include/Poco/Net/StreamSocket.h
+++ b/Net/include/Poco/Net/StreamSocket.h
@@ -257,12 +257,17 @@ class Net_API StreamSocket: public Socket
 		///
 		/// The preferred way for a socket to receive urgent data
 		/// is by enabling the SO_OOBINLINE option.
-
-	Poco::Int64 sendFile(FileInputStream &FileInputStream, Poco::UInt64 offset = 0);
+#ifdef POCO_HAVE_SENDFILE
+	IntPtr sendFile(FileInputStream &FileInputStream, UIntPtr offset = 0);
 		/// Sends file using system function
 		/// for posix systems - with sendfile[64](...)
 		/// for windows - with TransmitFile(...)
-
+		///
+		/// Returns the number of bytes sent, which may be
+		/// less than the number of bytes specified.
+		///
+		/// Throws NetException (or a subclass) in case of any errors.
+#endif
 	StreamSocket(SocketImpl* pImpl);
 		/// Creates the Socket and attaches the given SocketImpl.
 		/// The socket takes ownership of the SocketImpl.
diff --git a/Net/src/HTTPServerResponseImpl.cpp b/Net/src/HTTPServerResponseImpl.cpp
index a127b14c34..ce4fd5bf36 100644
--- a/Net/src/HTTPServerResponseImpl.cpp
+++ b/Net/src/HTTPServerResponseImpl.cpp
@@ -28,6 +28,8 @@
 #include "Poco/FileStream.h"
 #include "Poco/DateTimeFormatter.h"
 #include "Poco/DateTimeFormat.h"
+#include "Poco/Error.h"
+#include "Poco/Net/NetException.h"
 
 
 using Poco::File;
@@ -37,6 +39,7 @@ using Poco::StreamCopier;
 using Poco::OpenFileException;
 using Poco::DateTimeFormatter;
 using Poco::DateTimeFormat;
+using Poco::Error;
 using namespace std::string_literals;
 
 
@@ -129,7 +132,19 @@ void HTTPServerResponseImpl::sendFile(const std::string& path, const std::string
 		write(*_pStream);
 		if (_pRequest && _pRequest->getMethod() != HTTPRequest::HTTP_HEAD)
 		{
+#ifdef POCO_HAVE_SENDFILE
+			_pStream->flush(); // flush the HTTP headers to the socket, required by HTTP 1.0 and above
+
+			Poco::IntPtr sent = 0;
+			Poco::IntPtr offset = 0;
+			while (sent < length)
+			{
+				offset = sent;
+				sent += _session.socket().sendFile(istr, offset);
+			}
+#else
 			StreamCopier::copyStream(istr, *_pStream);
+#endif
 		}
 	}
 	else throw OpenFileException(path);
diff --git a/Net/src/SocketImpl.cpp b/Net/src/SocketImpl.cpp
index 34cad7d074..5a3c7b1197 100644
--- a/Net/src/SocketImpl.cpp
+++ b/Net/src/SocketImpl.cpp
@@ -56,7 +56,7 @@
 using sighandler_t = sig_t;
 #endif
 
-#if POCO_OS == POCO_OS_LINUX && !defined(POCO_EMSCRIPTEN)
+#if POCO_OS == POCO_OS_LINUX && defined(POCO_HAVE_SENDFILE) && !defined(POCO_EMSCRIPTEN)
 #include <sys/sendfile.h>
 #endif
 
@@ -1372,12 +1372,12 @@ void SocketImpl::error(int code, const std::string& arg)
 		throw IOException(NumberFormatter::format(code), arg, code);
 	}
 }
-
+#ifdef POCO_HAVE_SENDFILE
 #ifdef POCO_OS_FAMILY_WINDOWS
 Poco::Int64 SocketImpl::sendFile(FileInputStream &fileInputStream, Poco::UInt64 offset)
 {
 	FileIOS::NativeHandle fd = fileInputStream.nativeHandle();
-	Poco::UInt64 fileSize = fileInputStream.size();
+	UInt64 fileSize = fileInputStream.size();
 	std::streamoff sentSize = fileSize - offset;
 	LARGE_INTEGER offsetHelper;
 	offsetHelper.QuadPart = offset;
@@ -1388,7 +1388,8 @@ Poco::Int64 SocketImpl::sendFile(FileInputStream &fileInputStream, Poco::UInt64
 	overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 	if (overlapped.hEvent == nullptr)
 	{
-		return -1;
+		int err = GetLastError();
+		error(err, std::string("[sendfile error]") + Error::getMessage(err));
 	}
 	bool result = TransmitFile(_sockfd, fd, sentSize, 0, &overlapped, nullptr, 0);
 	if (!result)
@@ -1396,7 +1397,7 @@ Poco::Int64 SocketImpl::sendFile(FileInputStream &fileInputStream, Poco::UInt64
 		int err = WSAGetLastError();
 		if ((err != ERROR_IO_PENDING) && (WSAGetLastError() != WSA_IO_PENDING)) {
 			CloseHandle(overlapped.hEvent);
-			error(err, Error::getMessage(err));
+			error(err, std::string("[sendfile error]") + Error::getMessage(err));
 		}
 		WaitForSingleObject(overlapped.hEvent, INFINITE);
 	}
@@ -1404,9 +1405,9 @@ Poco::Int64 SocketImpl::sendFile(FileInputStream &fileInputStream, Poco::UInt64
 	return sentSize;
 }
 #else
-Poco::Int64 _sendfile(poco_socket_t sd, FileIOS::NativeHandle fd, Poco::UInt64 offset,std::streamoff sentSize)
+Int64 _sendfile(poco_socket_t sd, FileIOS::NativeHandle fd, UInt64 offset, std::streamoff sentSize)
 {
-	Poco::Int64 sent = 0;
+	Int64 sent = 0;
 #ifdef __USE_LARGEFILE64
 	sent = sendfile64(sd, fd, (off64_t *)&offset, sentSize);
 #else
@@ -1433,21 +1434,26 @@ Poco::Int64 _sendfile(poco_socket_t sd, FileIOS::NativeHandle fd, Poco::UInt64 o
 	return sent;
 }
 
-Poco::Int64 SocketImpl::sendFile(FileInputStream &fileInputStream, Poco::UInt64 offset)
+Int64 SocketImpl::sendFile(FileInputStream &fileInputStream, UInt64 offset)
 {
 	FileIOS::NativeHandle fd = fileInputStream.nativeHandle();
-	Poco::UInt64 fileSize = fileInputStream.size();
+	UInt64 fileSize = fileInputStream.size();
 	std::streamoff sentSize = fileSize - offset;
-	Poco::Int64 sent = 0;
+	Int64 sent = 0;
 	sighandler_t sigPrev = signal(SIGPIPE, SIG_IGN);
 	while (sent == 0)
 	{
 		errno = 0;
 		sent = _sendfile(_sockfd, fd, offset, sentSize);
+		if (sent < 0)
+		{
+			error(errno, std::string("[sendfile error]") + Error::getMessage(errno));
+		}
 	}
 	signal(SIGPIPE, sigPrev != SIG_ERR ? sigPrev : SIG_DFL);
 	return sent;
 }
 #endif // POCO_OS_FAMILY_WINDOWS
+#endif // POCO_HAVE_SENDFILE
 
 } } // namespace Poco::Net
diff --git a/Net/src/StreamSocket.cpp b/Net/src/StreamSocket.cpp
index 7741654ed7..806c56516a 100644
--- a/Net/src/StreamSocket.cpp
+++ b/Net/src/StreamSocket.cpp
@@ -212,10 +212,10 @@ void StreamSocket::sendUrgent(unsigned char data)
 {
 	impl()->sendUrgent(data);
 }
-
-Poco::Int64 StreamSocket::sendFile(FileInputStream &fileInputStream, Poco::UInt64 offset)
+#ifdef POCO_HAVE_SENDFILE
+IntPtr StreamSocket::sendFile(FileInputStream &fileInputStream, UIntPtr offset)
 {
 	return impl()->sendFile(fileInputStream, offset);
 }
-
+#endif
 } } // namespace Poco::Net
diff --git a/Net/testsuite/src/HTTPServerTest.cpp b/Net/testsuite/src/HTTPServerTest.cpp
index 3379188ca6..d39695e3b9 100644
--- a/Net/testsuite/src/HTTPServerTest.cpp
+++ b/Net/testsuite/src/HTTPServerTest.cpp
@@ -24,6 +24,9 @@
 #include "Poco/Net/HTTPServerSession.h"
 #include "Poco/Net/ServerSocket.h"
 #include "Poco/StreamCopier.h"
+#include "Poco/Path.h"
+#include "Poco/FileStream.h"
+#include "Poco/File.h"
 #include <sstream>
 
 
@@ -40,10 +43,15 @@ using Poco::Net::HTTPServerResponse;
 using Poco::Net::HTTPMessage;
 using Poco::Net::ServerSocket;
 using Poco::StreamCopier;
+using Poco::Path;
+using Poco::File;
+using Poco::FileOutputStream;
 
 
 namespace
 {
+	static const int sendFileSize = 64000;
+
 	class EchoBodyRequestHandler: public HTTPRequestHandler
 	{
 	public:
@@ -105,7 +113,29 @@ namespace
 			response.sendBuffer(data.data(), data.length());
 		}
 	};
-
+	
+	class FileRequestHandler: public HTTPRequestHandler
+	{
+	public:
+		void handleRequest(HTTPServerRequest& request, HTTPServerResponse& response)
+		{
+			std::string payload(sendFileSize, 'x');
+			Poco::Path testFilePath = Poco::Path::temp().append("test.http.server.sendfile.txt");
+			const std::string fileName = testFilePath.toString();
+			{
+				File f(fileName);
+				if (f.exists())
+				{
+					f.remove();
+				}
+			}
+			FileOutputStream fout(fileName);
+			fout << payload;
+			fout.close();
+			response.sendFile(fileName, "text/plain");
+		}
+	};
+	
 	class TrailerRequestHandler: public HTTPRequestHandler
 	{
 	public:
@@ -138,8 +168,10 @@ namespace
 				return new BufferRequestHandler;
 			else if (request.getURI() == "/trailer")
 				return new TrailerRequestHandler;
+			else if (request.getURI() == "/file")
+				return new FileRequestHandler;
 			else
-				return 0;
+				return nullptr;
 		}
 	};
 }
@@ -534,6 +566,26 @@ void HTTPServerTest::testBuffer()
 	assertTrue (rbody == "xxxxxxxxxx");
 }
 
+void HTTPServerTest::testFile()
+{
+	std::string payload(sendFileSize, 'x');
+	
+	ServerSocket svs(0);
+	HTTPServerParams* pParams = new HTTPServerParams;
+	pParams->setKeepAlive(false);
+	HTTPServer srv(new RequestHandlerFactory, svs, pParams);
+	srv.start();
+	
+	HTTPClientSession cs("127.0.0.1", svs.address().port());
+	HTTPRequest request("GET", "/file");
+	cs.sendRequest(request);
+	HTTPResponse response;
+	std::string rbody;
+	cs.receiveResponse(response) >> rbody;
+	assertTrue (response.getStatus() == HTTPResponse::HTTP_OK);
+	assertTrue (rbody == payload);
+}
+
 
 void HTTPServerTest::testChunkedTrailer()
 {
@@ -585,6 +637,7 @@ CppUnit::Test* HTTPServerTest::suite()
 	CppUnit_addTest(pSuite, HTTPServerTest, testAuth);
 	CppUnit_addTest(pSuite, HTTPServerTest, testNotImpl);
 	CppUnit_addTest(pSuite, HTTPServerTest, testBuffer);
+	CppUnit_addTest(pSuite, HTTPServerTest, testFile);
 	CppUnit_addTest(pSuite, HTTPServerTest, testChunkedTrailer);
 
 	return pSuite;
diff --git a/Net/testsuite/src/HTTPServerTest.h b/Net/testsuite/src/HTTPServerTest.h
index 3ba58b24b8..84e4f550b4 100644
--- a/Net/testsuite/src/HTTPServerTest.h
+++ b/Net/testsuite/src/HTTPServerTest.h
@@ -38,6 +38,7 @@ class HTTPServerTest: public CppUnit::TestCase
 	void testAuth();
 	void testNotImpl();
 	void testBuffer();
+	void testFile();
 	void testChunkedTrailer();
 
 	void setUp();
diff --git a/Net/testsuite/src/SocketStreamTest.cpp b/Net/testsuite/src/SocketStreamTest.cpp
index 5a453b4449..aef327a3dc 100644
--- a/Net/testsuite/src/SocketStreamTest.cpp
+++ b/Net/testsuite/src/SocketStreamTest.cpp
@@ -124,6 +124,7 @@ void SocketStreamTest::testEOF()
 	ss.close();
 }
 
+#ifdef POCO_HAVE_SENDFILE
 void SocketStreamTest::testSendFile()
 {
 	const int fileSize = 64000;
@@ -147,11 +148,11 @@ void SocketStreamTest::testSendFile()
 	
 	SocketStream str(ss);
 
-	Poco::UInt64 offset = 0;
-	Poco::Int64 sent = 0;
+	Poco::UIntPtr offset = 0;
+	Poco::IntPtr  sent = 0;
 	try
 	{
-	sent = ss.sendFile(fin);
+		sent = ss.sendFile(fin);
 	}
 	catch (Poco::NotImplementedException &)
 	{
@@ -162,8 +163,7 @@ void SocketStreamTest::testSendFile()
 	while (sent < fileSize)
 	{
 		offset = sent;
-		sent = ss.sendFile(fin, offset);
-		assertTrue(sent >= 0);
+		sent += ss.sendFile(fin, offset);
 	}
 	str.flush();
 	assertTrue (str.good());
@@ -180,6 +180,7 @@ void SocketStreamTest::testSendFile()
 	File f(fileName);
 	f.remove();
 }
+#endif
 
 void SocketStreamTest::setUp()
 {
@@ -198,7 +199,9 @@ CppUnit::Test* SocketStreamTest::suite()
 	CppUnit_addTest(pSuite, SocketStreamTest, testStreamEcho);
 	CppUnit_addTest(pSuite, SocketStreamTest, testLargeStreamEcho);
 	CppUnit_addTest(pSuite, SocketStreamTest, testEOF);
+#ifdef POCO_HAVE_SENDFILE
 	CppUnit_addTest(pSuite, SocketStreamTest, testSendFile);
+#endif
 
 	return pSuite;
 }
diff --git a/Net/testsuite/src/SocketStreamTest.h b/Net/testsuite/src/SocketStreamTest.h
index c97a77e6f2..69d5172adf 100644
--- a/Net/testsuite/src/SocketStreamTest.h
+++ b/Net/testsuite/src/SocketStreamTest.h
@@ -27,7 +27,9 @@ class SocketStreamTest: public CppUnit::TestCase
 	void testStreamEcho();
 	void testLargeStreamEcho();
 	void testEOF();
+#ifdef POCO_HAVE_SENDFILE
 	void testSendFile();
+#endif
 
 	void setUp();
 	void tearDown();