From 230430c4e9c8fcb27db7992a740106fc20bbbcab Mon Sep 17 00:00:00 2001
From: Jae Stutzman <jaebird@gmail.com>
Date: Mon, 23 Jan 2017 22:21:49 -0600
Subject: [PATCH] Clears potential garbage data in read buffer prior to command
 being sent

---
 kenwood/kenwood.c |  9 ++++++++-
 src/network.c     | 23 +++++++++++++++++++++++
 src/network.h     |  1 +
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/kenwood/kenwood.c b/kenwood/kenwood.c
index d047eac25..ebb3401fd 100644
--- a/kenwood/kenwood.c
+++ b/kenwood/kenwood.c
@@ -33,6 +33,7 @@
 #include <ctype.h>
 
 #include "hamlib/rig.h"
+#include "network.h"
 #include "serial.h"
 #include "misc.h"
 #include "register.h"
@@ -242,7 +243,13 @@ int kenwood_transaction(RIG *rig, const char *cmdstr, char *data, size_t datasiz
         len++;
       }
 
-      serial_flush(&rs->rigport);
+      /* flush anything in the read buffer before command is sent */
+      if (rs->rigport.type.rig == RIG_PORT_NETWORK || rs->rigport.type.rig == RIG_PORT_UDP_NETWORK) {
+            network_flush(&rs->rigport);
+      } else {
+          serial_flush(&rs->rigport);
+      }
+
       retval = write_block(&rs->rigport, cmd, len);
 
       free(cmd);
diff --git a/src/network.c b/src/network.c
index 9e939e4bf..3a48557f9 100644
--- a/src/network.c
+++ b/src/network.c
@@ -44,6 +44,7 @@
 #include <sys/time.h>
 #include <sys/types.h>
 #include <signal.h>
+#include <sys/ioctl.h>
 
 
 #ifdef HAVE_NETINET_IN_H
@@ -73,6 +74,8 @@
 static int wsstarted;
 #endif
 
+#define NET_BUFFER_SIZE 64
+
 static void handle_error (enum rig_debug_level_e lvl, const char *msg)
 {
 	int e;
@@ -103,6 +106,26 @@ static void handle_error (enum rig_debug_level_e lvl, const char *msg)
 #endif
 }
 
+/**
+ * \brief Clears any data in the read buffer of the socket
+ *
+ * \param rp Port data structure
+ */
+void network_flush(hamlib_port_t* rp)
+{
+  int len = 0;
+  char buffer[NET_BUFFER_SIZE] = { 0 };
+  for (;;) {
+    ioctl(rp->fd, FIONREAD, &len);
+    if (len > 0) {
+      len = read(rp->fd, &buffer, len < NET_BUFFER_SIZE ? len : NET_BUFFER_SIZE);
+      rig_debug(RIG_DEBUG_WARN, "Network data cleared: %s\n", buffer);
+    } else {
+      break;
+    }
+  }
+}
+
 /**
  * \brief Open network port using rig.state data
  *
diff --git a/src/network.h b/src/network.h
index c3cc6a8d9..1411d72a4 100644
--- a/src/network.h
+++ b/src/network.h
@@ -30,6 +30,7 @@ __BEGIN_DECLS
 /* Hamlib internal use, see rig.c */
 int network_open(hamlib_port_t *p, int default_port);
 int network_close(hamlib_port_t *rp);
+void network_flush(hamlib_port_t *rp);
 
 __END_DECLS