diff --git a/sipcap/sipcap.c b/sipcap/sipcap.c
index 6cb44e3..5fce616 100644
--- a/sipcap/sipcap.c
+++ b/sipcap/sipcap.c
@@ -1,8 +1,84 @@
+#include <stdlib.h>
 #include <stdio.h>
 #include <getopt.h>
 #include <pcap.h>
+#include <netinet/ip.h>
+#include <arpa/inet.h>
+
+#define SIPCAP_VERSION 1.2
+
+#define ETHER_TYPE_IP (0x0800)
+#define ETHER_TYPE_8021Q (0x8100)
+
+
+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");
+	printf("\n");
+	if (quit) exit(quit);
+}
+
+void error(char *msg) {
+	fprintf(stderr, "Error: %s\n", msg);
+	exit(1);
+}
 
 int main(int argc, char *argv[])
 {
-	return(0);
+	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;
+
+	while ((opt = getopt (argc, argv, "i:f:e:o:s:h")) != -1)
+		switch (opt) {
+			case 'h':
+				help(0);
+				break;
+			case 'i':
+				live_pcap = 1;
+				if (offline_pcap) error("-i and -f are mutually exclusive");
+				if (optarg == NULL) help(1);
+				pcap_interface = 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;
+				break;
+			case 'e':
+				has_expression = 1;
+				if (optarg == NULL) help(1);
+				break;
+			case 'o':
+				output_to_file = 1;
+				if (optarg == NULL) help(1);
+				out_file = optarg;
+				break;
+			case 's':
+				if (optarg == NULL) help(1);
+				snaplen = atoi(optarg);
+				printf("snaplen is %d\n", snaplen);
+				break;
+		}     
+
+	if (!live_pcap && !offline_pcap) help(1);
+	
+	if (live_pcap) {
+		error("live capture not implemented");
+	} else {
+		pcap = pcap_open_offline(pcap_file, errbuf);
+		if (pcap == NULL) error("cannot open capture file");
+	}
+
+	pcap_close(pcap);
+	exit(0);
 }