--- OLD
+++ NEW
@@ -322,12 +322,20 @@
         if (!FD_ISSET(i, fds))
             continue;
 
+        /* If we are sending a large amount of data, we might momentarily run out of
+           send space and get a -1 + EAGAIN when we send. We could handle it ourselves,
+           or we could just mark the socket as blocking, and the OS will handle it for us. */
+        block_socket(i);
+
         fdn = get_fdinfo(fdlist, i);
         if (fdinfo_send(fdn, msg, size) <= 0) {
             if (o.debug > 1)
                 logdebug("Error sending to fd %d: %s.\n", i, socket_strerror(socket_errno()));
             ret = -1;
         }
+
+        /* Return to its former state when we're done with the send */
+        unblock_socket(i);
     }
 
     ncat_log_send(msg, size);