diff --git a/README.md b/README.md
index ea51344..ba536b3 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,7 @@ to RF using software-defined radio (SDR) platforms, such as
 ### Building with GCC
 
 ```
-$ gcc gpssim.c -lm -O3 -o gps-sdr-sim
+$ gcc gpssim.c -lm -lpthread -O3 -o gps-sdr-sim
 ```
 
 ### Realtime by Gnuradio
diff --git a/gpssim.c b/gpssim.c
index dde6f09..988d5ff 100644
--- a/gpssim.c
+++ b/gpssim.c
@@ -1661,10 +1661,10 @@ void usage(void)
 		"  -s <frequency>   Sampling frequency [Hz] (default: 2600000)\n"
 		"  -b <iq_bits>     I/Q data format [1/8/16] (default: 16)\n"
 		"  -i               Disable ionospheric delay for spacecraft scenario\n"
-		"  -v               Show details about simulated channels\n",
-		"  -n <port>        Use TCP connect to Gnuradio TCP-Source for\n realtime simulation.\n",
+		"  -v               Show details about simulated channels\n"
+		"  -n <port>        Use TCP connect to Gnuradio TCP-Source for\n realtime simulation.\n"
 		"-w               Connect with map server(/mapserver/mapper.py) by udp on port 5678.\n",
-		(USER_MOTION_SIZE)/10.0,STATIC_MAX_DURATION);
+		(double)((USER_MOTION_SIZE)/10.0),(int)STATIC_MAX_DURATION);
 
 	return;
 }
@@ -1850,9 +1850,11 @@ int main(int argc, char *argv[])
 			sscanf(optarg,"%hd",&port);
 			
 			usesocket=true;
+			break;
 		case  'w':
 			staticLocationMode = TRUE;
 			webflag=1;
+			break;
 			
 		default:
 			break;
diff --git a/socket.c b/socket.c
index 1e23858..3076989 100644
--- a/socket.c
+++ b/socket.c
@@ -8,7 +8,7 @@
 #include <stdlib.h>
 #include <fcntl.h>
 #include <sys/shm.h>
-
+#include <sys/time.h>
 
 
 
@@ -57,10 +57,10 @@ int udpinit(short port){
 }
 int udprecv(int s,void *dataa,int siz){
 	struct sockaddr from;
-	return recvfrom(s, dataa, siz, 0,&from,sizeof(from));
+	return recvfrom(s, dataa, siz, 0,&from,0);
 }
 
-double llhr[3]={39.68,139,76,10};
+double llhr[3]={39.68,139,76};
 
 void threadrecv(){
 	printf("listing\n");