diff --git a/slsDetectorSoftware/slsReceiver/slsReceiverFunctionList.cpp b/slsDetectorSoftware/slsReceiver/slsReceiverFunctionList.cpp
index 867f8d6cc..61213346d 100644
--- a/slsDetectorSoftware/slsReceiver/slsReceiverFunctionList.cpp
+++ b/slsDetectorSoftware/slsReceiver/slsReceiverFunctionList.cpp
@@ -20,13 +20,10 @@
 #include <sys/socket.h>		// socket(), bind(), listen(), accept(), shut down
 #include <arpa/inet.h>		// sock_addr_in, htonl, INADDR_ANY
 #include <stdlib.h>			// exit()
-
 #include <iomanip>			//set precision
+#include <sys/mman.h>		//munmap
 
 
-//#include <sched.h>			//sched_idle
-//#include <fcntl.h>			//posix_fadvice
-
 #include <string.h>
 #include <iostream>
 using namespace std;
@@ -248,7 +245,7 @@ int slsReceiverFunctionList::startReceiver(){
 			cout << "ERROR: Could not prioritize threads. You need to be super user for that." << endl;
 		if (pthread_setschedparam(writing_thread, policy, &write_param) == EPERM)
 			cout << "ERROR: Could not prioritize threads. You need to be super user for that." << endl;
-		if (pthread_setschedparam(pthread_self(),policy , &tcp_param) == EPERM)
+		if (pthread_setschedparam(pthread_self(),5 , &tcp_param) == EPERM)
 			cout << "ERROR: Could not prioritize threads. You need to be super user for that." << endl;
 
 
@@ -319,8 +316,9 @@ int slsReceiverFunctionList::startListening(){
 	//  very end of the program.
 	do {
 
-		if (strchr(eth,'.')!=NULL) strcpy(eth,"");
 
+		//creating udp socket
+		if (strchr(eth,'.')!=NULL) strcpy(eth,"");
 		if(!strlen(eth)){
 			cout<<"warning:eth is empty.listening to all"<<endl;
 			udpSocket = new genericSocket(server_port,genericSocket::UDP,bufferSize/packetsPerFrame,packetsPerFrame);
@@ -328,7 +326,6 @@ int slsReceiverFunctionList::startListening(){
 			cout<<"eth:"<<eth<<endl;
 			udpSocket = new genericSocket(server_port,genericSocket::UDP,bufferSize/packetsPerFrame,packetsPerFrame,eth);
 		}
-
 		if (udpSocket->getErrorStatus()){
 #ifdef VERBOSE
 			std::cout<< "Could not create UDP socket "<< server_port  << std::endl;
@@ -344,7 +341,7 @@ int slsReceiverFunctionList::startListening(){
 				fifofree->pop(buffer);
 
 				//receiver 2 half frames / 1 short frame / 40 moench frames
-				rc = udpSocket->ReceiveDataOnly(buffer,bufferSize);//sizeof(buffer));
+				rc = udpSocket->ReceiveDataOnly(buffer,bufferSize);
 				if( rc < 0)
 					cerr << "recvfrom() failed" << endl;
 
@@ -413,6 +410,9 @@ int slsReceiverFunctionList::startWriting(){
 	cout << "In startWriting()" <<endl;
 #endif
 
+
+	void *address;
+	int memsize = bufferSize*maxFramesPerFile;
 	char *wbuf;
 	int sleepnumber=0;
 
@@ -422,96 +422,97 @@ int slsReceiverFunctionList::startWriting(){
 	if(sfilefd) sfilefd=0;
 	strcpy(savefilename,"");
 
+
 	cout << "Max Frames Per File:" << maxFramesPerFile << endl;
 	if (writeReceiverData)
 		cout << "Note: Data Write has been defined exernally" << endl;
 	if(nFrameToGui)
 		cout << " Not implemented yet: Sending every " << nFrameToGui << "th frame to gui" <<  endl;
 
-	cout << "Ready!" << endl;
 
 	//by default, we read/write everything
 	cbAction=2;
-
-	//acquisition start
+	//acquisition start call back returns enable write
 	if (startAcquisitionCallBack)
 		cbAction=startAcquisitionCallBack(filePath,fileName,fileIndex,bufferSize,pStartAcquisition);
-
-
-
-
-
-
-
 	if(enableFileWrite==0 || cbAction==0)
 		cout << endl << "Note: Data will not be saved" << endl;
 
-	//create file name
-	if(frameIndexNeeded==-1)		sprintf(savefilename, "%s/%s_%d.raw", filePath,fileName,fileIndex);
-	else							sprintf(savefilename, "%s/%s_f%012d_%d.raw", filePath,fileName,framesCaught,fileIndex);
-
-
-	//start writing
-	if(enableFileWrite || cbAction>0){
-		sfilefd = fopen((const char *) (savefilename), "w");
-		cout << savefilename << endl;
-		//posix_fadvise(fileno(sfilefd),0,0,POSIX_FADV_DONTNEED|POSIX_FADV_SEQUENTIAL);
-	}
-
-
 
+	cout << "Ready!" << endl;
 	while(listening_thread_running || (!fifo->isEmpty())){
 
-		//when it reaches maxFramesPerFile,start writing new file
-		if (framesInFile == maxFramesPerFile) {
+		//start a new file
+		if ((framesInFile == maxFramesPerFile)  || (strlen(savefilename) == 0)){
 
 			//create file name
 			if(frameIndexNeeded==-1)	sprintf(savefilename, "%s/%s_%d.raw", filePath,fileName,fileIndex);
 			else						sprintf(savefilename, "%s/%s_f%012d_%d.raw", filePath,fileName,framesCaught,fileIndex);
 
-			//start writing in new file
 			if(enableFileWrite || cbAction>0){
-				//fsync(fileno(sfilefd));
-				fclose(sfilefd);
-				sfilefd = fopen((const char *) (savefilename), "w");
-				//posix_fadvise(fileno(sfilefd),0,0,POSIX_FADV_DONTNEED|POSIX_FADV_SEQUENTIAL);
+				//sync file and close fd
+				if(sfilefd) {
+					msync(address,memsize,  MS_ASYNC);
+					munmap(address,memsize);
+					fclose(sfilefd);
+				}
+
+				//create file , truncate size and map file to memory
+				if (NULL == (sfilefd = fopen((const char *) (savefilename), "w+"))){
+					cout << "Error: Could not create file " << savefilename << endl;
+					break;
+				}
+				if (-1 == ftruncate(fileno(sfilefd),memsize)) {
+					perror("Error:Could not truncate file:");
+					break;
+				}
+				address = mmap(NULL,memsize,PROT_READ|PROT_WRITE,MAP_SHARED,fileno(sfilefd),0);
+				if(address == MAP_FAILED)
+					perror("Error: Could not map file to memory:");
 			}
 
-			//currframenum=(int)(*((int*)latestData));
-			cout << savefilename << "\tpacket loss " << fixed << setprecision(4) << ((currframenum-prevframenum-(packetsPerFrame*framesInFile))/(double)(packetsPerFrame*framesInFile))*100.000 << "%\t\t"
-					"framenum " << currframenum << "\t\t"
-					"p " << prevframenum << endl;
+			//printing packet losses and file names
+			if(prevframenum == 0)
+				cout << savefilename << endl;
+			else{
+				cout << savefilename << "\tpacket loss " << fixed << setprecision(4) << ((currframenum-prevframenum-(packetsPerFrame*framesInFile))/(double)(packetsPerFrame*framesInFile))*100.000 << "%\t\t"
+						"framenum " << currframenum << "\t\t"
+						"p " << prevframenum << endl;
 
-			prevframenum=currframenum;
-			framesInFile = 0;
+				prevframenum=currframenum;
+				framesInFile = 0;
+			}
 		}
 
 
 
-		//actual writing from fifo
+		//pop fifo
 		if(!fifo->isEmpty()){
 
 			if(fifo->pop(wbuf)){
 				framesCaught++;
 				totalFramesCaught++;
-				currframenum = (int)(*((int*)wbuf));//cout<<"curreframenm:"<<currframenum<<endl;
+				currframenum = (int)(*((int*)wbuf));//cout<<"**************curreframenm:"<<currframenum<<endl;
 
 				//write data
 				if(enableFileWrite){
+					//write data call back
 					if (writeReceiverData) {
 						writeReceiverData(wbuf,bufferSize, sfilefd, pwriteReceiverDataArg);
 					}
+					//write data call back
 					if (cbAction<2) {
 						rawDataReadyCallBack(currframenum, wbuf,sfilefd, guiData,pRawDataReady);
-					} else {
+					}
+					//default writing to file
+					else {
 						if(sfilefd)
-							fwrite(wbuf, 1, bufferSize, sfilefd);
+							memcpy(address,wbuf, bufferSize);
 						else{
 							cout << "You do not have permissions to overwrite: " << savefilename << endl;
 							usleep(50000);
 						}
 					}
-
 				}
 
 
@@ -527,29 +528,27 @@ int slsReceiverFunctionList::startWriting(){
 
 
 				framesInFile++;
-				//	delete [] dataWriteFrame->buffer;
 				fifofree->push(wbuf);
 			}
-			//	delete dataWriteFrame;
 		}
 		else{//cout<<"************************fifo empty**********************************"<<endl;
 			sleepnumber++;
 			usleep(50000);
 		}
 	}
-
+	listening_thread_running = 0;
 	cout << "Total Frames Caught:"<< totalFramesCaught << endl;
-	//close file
-	if(sfilefd)
+	//sync file and close fd, memsize is still for maxframes because of truncate
+	if(sfilefd){
+		msync(address,memsize,  MS_ASYNC);
+		munmap(address,memsize);
 		fclose(sfilefd);
-	//{ fsync(fileno(sfilefd));fclose(sfilefd);}
+	}
 #ifdef VERBOSE
 	cout << "sfield:" << (int)sfilefd << endl;
 #endif
 
-
-
-	//acquistion over
+	//acquistion over call back
 	if (acquisitionFinishedCallBack)
 		acquisitionFinishedCallBack(totalFramesCaught, pAcquisitionFinished);
 
diff --git a/slsDetectorSoftware/slsReceiver/slsReceiverFunctionList.h b/slsDetectorSoftware/slsReceiver/slsReceiverFunctionList.h
index 0377004c2..2b195330a 100644
--- a/slsDetectorSoftware/slsReceiver/slsReceiverFunctionList.h
+++ b/slsDetectorSoftware/slsReceiver/slsReceiverFunctionList.h
@@ -291,7 +291,7 @@ private:
 	/** short frames */
 	int shortFrame;
 
-	/** buffer size can be 1286*2 or 518 */
+	/** buffer size can be 1286*2 or 518 or 1286*40 */
 	int bufferSize;
 
 	/** number of packets per frame*/