diff --git a/rlgwebd.js b/rlgwebd.js
index 71a3d94..6f7ced6 100755
--- a/rlgwebd.js
+++ b/rlgwebd.js
@@ -258,6 +258,7 @@ function DglSession(filename) {
   /* Flag to prevent multiple handlers from reading simultaneously and
    * getting into a race. */
   this.reading = false;
+  this.rpos = 0;
   this.framebuf = new Buffer(1024);
   this.frameoff = 0;
   this.framepush = function(chunk) {
@@ -286,24 +287,36 @@ function DglSession(filename) {
       return;
     this.reading = true;
     var header = new Buffer(12);
-    fs.read(ss.fd, header, 0, 12, null, function (err, n, buf) {
+    fs.read(ss.fd, header, 0, 12, ss.rpos, function (err, n, buf) {
       /* Stop recursion if end of file has been reached. */
       if (err || n < 12) {
+        if (!err && n > 0) {
+          tslog("DGL %s: expected 12-byte header, got %d", ss.tag(), n);
+        }
         ss.reading = false;
         return;
       }
+      ss.rpos += 12;
       var datalen = buf.readUInt32LE(8);
       //tslog("Allocating %d bytes", datalen);
+      if (datalen > 16384) {
+        tslog("DGL %s: looking for %d bytes", ss.tag(), datalen);
+      }
       var databuf = new Buffer(datalen);
-      fs.read(ss.fd, databuf, 0, datalen, null, function (err, n, buf) {
-        ss.reading = false;
+      fs.read(ss.fd, databuf, 0, datalen, ss.rpos, function (err, n, buf) {
         if (err || n < datalen) {
+          /* Next time, read the header again. */
+          ss.rpos -= 12;
+          ss.reading = false;
+          tslog("DGL %s: expected %d bytes, got %d", ss.tag(), datalen, n);
           return;
         }
+        ss.rpos += n;
+        ss.reading = false;
         /* Process the data */
         ss.framepush(buf);
         ss.emit("data", buf);
-        tslog("DGL %s: %d bytes", ss.tag(), buf.length);
+        //tslog("DGL %s: %d bytes", ss.tag(), buf.length);
         /* Recurse. */
         ss.readchunk();
       });