diff --git a/README.md b/README.md
index 8aad3cf..7cc6368 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,8 @@
 # tftp-proxy
 A TFTP server that proxies request to an HTTP backend if a file is not found.
+
+# How to build
+    go build tftp.go
+
+# How to run
+    ./tftp -url=http://example.com -dir=/var/lib/tftpboot &
diff --git a/tftp.go b/tftp.go
new file mode 100644
index 0000000..737d9f4
--- /dev/null
+++ b/tftp.go
@@ -0,0 +1,84 @@
+package main
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/pin/tftp"
+)
+
+var url string
+var dir string
+
+// readHandler is called when client starts file download from server
+func readHandler(filename string, rf io.ReaderFrom) error {
+
+	if _, err := os.Stat(filename); err == nil {
+		file, err := os.Open(filename)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%v\n", err)
+			return err
+		}
+
+		fi, err := file.Stat()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%v\n", err)
+			return err
+		}
+
+		rf.(tftp.OutgoingTransfer).SetSize(fi.Size())
+		n, err := rf.ReadFrom(file)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%v\n", err)
+			return err
+		}
+
+		fmt.Printf("%s %d bytes sent\n", filename, n)
+	} else { // File not found locally. Proxying the request.
+		fileUrl := url + "/" + filename
+		resp, err := http.Get(fileUrl)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%v\n", err)
+			return err
+		}
+		defer resp.Body.Close()
+
+		if resp.StatusCode != 200 {
+			return errors.New(fmt.Sprintf("Received status code: %d", resp.StatusCode))
+		}
+
+		rf.(tftp.OutgoingTransfer).SetSize(resp.ContentLength)
+		n, err := rf.ReadFrom(resp.Body)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%v\n", err)
+			return err
+		}
+
+		fmt.Printf("%s %d bytes sent\n", filename, n)
+	}
+
+	return nil
+}
+
+func main() {
+	flag.StringVar(&dir, "dir", "/var/lib/tftpboot", "The directory to serve files from. For example /var/lib/tftpboot")
+	flag.StringVar(&url, "url", "http://example.com", "The URL to proxy requests to. For example http://example.com")
+	flag.Parse()
+
+	// Change dir to the default tftp directory
+	os.Chdir(dir)
+
+	// use nil in place of handler to disable read or write operations
+	s := tftp.NewServer(readHandler, nil)
+	s.SetTimeout(5 * time.Second)  // optional
+	err := s.ListenAndServe(":69") // blocks until s.Shutdown() is called
+	if err != nil {
+		fmt.Fprintf(os.Stdout, "server: %v\n", err)
+		os.Exit(1)
+	}
+}