diff --git a/sipcap/sipcap.c b/sipcap/sipcap.c
index 5fce616..9d95116 100644
--- a/sipcap/sipcap.c
+++ b/sipcap/sipcap.c
@@ -10,9 +10,20 @@
 #define ETHER_TYPE_IP (0x0800)
 #define ETHER_TYPE_8021Q (0x8100)
 
+// Global Vars
+int pkt_count = 0;
+int live_pcap = 0;
+int offline_pcap = 0;
+int has_expression = 0;
+int output_to_file = 0;
+int snaplen = 0;
+char errbuf[PCAP_ERRBUF_SIZE];
+char *capfile, *capdev, *capture_expression, *out_file;
+
 
 void help(int quit)
 {
+
 	printf("sipcap - version %.2f\n\n", SIPCAP_VERSION);
 	printf("Usage: sipcap [-i <interface>|-f <pcapfile>] [-e expression] [-o outfile] \n");
 	printf("              [-s snaplen] [-h]\n");
@@ -21,22 +32,16 @@ void help(int quit)
 }
 
 void error(char *msg) {
+
 	fprintf(stderr, "Error: %s\n", msg);
 	exit(1);
 }
 
-int main(int argc, char *argv[])
-{
-	pcap_t *pcap;
-	char errbuf[PCAP_ERRBUF_SIZE];
-	int opt;
-	int live_pcap = 0;
-	int offline_pcap = 0;
-	int has_expression = 0;
-	int output_to_file = 0;
-	int snaplen = 0;
-	char *pcap_file, *pcap_interface, *capture_expression, *out_file;
+void parse_options(int argc, char *argv[]) {
 
+	// TODO: Add "-c" option that stops after capturing n packets
+
+	int opt;
 	while ((opt = getopt (argc, argv, "i:f:e:o:s:h")) != -1)
 		switch (opt) {
 			case 'h':
@@ -46,17 +51,18 @@ int main(int argc, char *argv[])
 				live_pcap = 1;
 				if (offline_pcap) error("-i and -f are mutually exclusive");
 				if (optarg == NULL) help(1);
-				pcap_interface = optarg;
+				capdev = optarg;
 				break;
 			case 'f':
 				offline_pcap = 1;
 				if (live_pcap) error("-i and -f are mutually exclusive");
 				if (optarg == NULL) help(1);
-				pcap_file = optarg;
+				capfile = optarg;
 				break;
 			case 'e':
 				has_expression = 1;
 				if (optarg == NULL) help(1);
+				capture_expression = optarg;
 				break;
 			case 'o':
 				output_to_file = 1;
@@ -66,19 +72,50 @@ int main(int argc, char *argv[])
 			case 's':
 				if (optarg == NULL) help(1);
 				snaplen = atoi(optarg);
-				printf("snaplen is %d\n", snaplen);
 				break;
-		}     
+		}	
+
+	if (!live_pcap && !offline_pcap) help(1);	
+}
+
+void process_packet(u_char *args, const struct pcap_pkthdr *header, const u_char *packet) {
+
+	// we do actual packet processing here
+	pkt_count++;
+}
+
+int main(int argc, char *argv[])
+{
+	pcap_t *pcap;
+	const u_char *packet;
+	struct pcap_pkthdr header;
+	struct bpf_program fp;
+	bpf_u_int32 devnet, devmask;
+
+	parse_options(argc, argv);
 
-	if (!live_pcap && !offline_pcap) help(1);
-	
 	if (live_pcap) {
-		error("live capture not implemented");
+		 if (pcap_lookupnet(capdev, &devnet, &devmask, errbuf) == -1) {
+			 fprintf(stderr, "WARNING: Can't get netmask for device %s\n", capdev);
+			 devnet = 0;
+			 devmask = 0;
+		 }
+
+		pcap = pcap_open_live(capdev, BUFSIZ, 1, 1000, errbuf);
+
 	} else {
-		pcap = pcap_open_offline(pcap_file, errbuf);
-		if (pcap == NULL) error("cannot open capture file");
+		pcap = pcap_open_offline(capfile, errbuf);
 	}
 
+	if (has_expression) {
+		if (pcap_compile(pcap, &fp, capture_expression, 0, devnet) == -1) error(pcap_geterr(pcap));
+		if (pcap_setfilter(pcap, &fp) == -1) error(pcap_geterr(pcap)); 
+	}
+
+	if (pcap == NULL) error(errbuf);
+
+	pcap_loop(pcap, -1, &process_packet, NULL);
+	printf("finished processing %d packets\n", pkt_count);
 	pcap_close(pcap);
 	exit(0);
 }