diff --git a/test_filtering.cpp b/test_filtering.cpp
new file mode 100644
index 0000000..c6e6e97
--- /dev/null
+++ b/test_filtering.cpp
@@ -0,0 +1,50 @@
+#include <stdio.h>
+#include <iostream>
+#include <pcap.h>
+
+// Initalize variables.
+
+using namespace std;
+
+pcap_t *handle;                 /* Session handle */
+string dev;             /* Device to sniff on */
+char errbuf[PCAP_ERRBUF_SIZE];  /* Error string */
+struct bpf_program fp;          /* The compiled filter expression */
+char filter_exp[] = "port 23";	/* The filter expression */
+bpf_u_int32 mask;               /* The netmask of our sniffing device */
+bpf_u_int32 net;                /* The IP of our sniffing device */
+
+int main()
+{
+	char *dev, errbuf[PCAP_ERRBUF_SIZE];
+
+    dev = pcap_lookupdev(errbuf);
+	
+    if (dev == NULL) {
+		fprintf(stderr, "Couldn't find default device: %s\n", errbuf);
+		return(2);
+	}
+    
+    if(pcap_lookupnet(dev, &net, &mask, errbuf) == -1) {
+        fprintf(stderr, "Can't get netmask for device %s\n", dev);
+        net = 0;
+        mask = 0;
+    }
+
+    handle = pcap_open_live(dev, BUFSIZ, 1, 1000, errbuf);
+
+    if(handle == NULL) {
+        fprintf(stderr, "Couldn't open device %s: %s\n", dev, errbuf);
+        return(2);
+    }
+
+    if(pcap_compile(handle, &fp, filter_exp, 0, net) == -1) {
+        fprintf(stderr, "Couldn't parse filter %s: %s\n", filter_exp, pcap_geterr(handle));
+        return(2);
+    }
+
+    if(pcap_setfilter(handle, &fp) == -1) {
+        fprintf(stderr, "Couldn't install filter %s: %s\n", filter_exp, pcap_geterr(handle));
+        return(2);
+    }
+}