diff --git a/src/nettnc.c b/src/nettnc.c
new file mode 100644
index 0000000..9b95ab1
--- /dev/null
+++ b/src/nettnc.c
@@ -0,0 +1,490 @@
+
+//
+//    This file is part of Dire Wolf, an amateur radio packet TNC.
+//
+//    Copyright (C) 2024  John Langner, WB2OSZ
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU General Public License as published by
+//    the Free Software Foundation, either version 2 of the License, or
+//    (at your option) any later version.
+//
+//    This program is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU General Public License for more details.
+//
+//    You should have received a copy of the GNU General Public License
+//    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+
+
+/*------------------------------------------------------------------
+ *
+ * Module:      nettnc.c
+ *
+ * Purpose:   	Attach to Network KISS TNC(s) for NCHANNEL config file item(s).
+ *		
+ * Description:	Called once at application start up.
+ *
+ *---------------------------------------------------------------*/
+
+
+#include "direwolf.h"		// Sets _WIN32_WINNT for XP API level needed by ws2tcpip.h
+
+#if __WIN32__
+#include <winsock2.h>
+#include <ws2tcpip.h>  		// _WIN32_WINNT must be set to 0x0501 before including this
+#else 
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <errno.h>
+#endif
+
+#include <unistd.h>
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+#include <time.h>
+#include <ctype.h>
+
+#include "textcolor.h"
+#include "audio.h"		// configuration.
+#include "kiss.h"
+#include "dwsock.h"		// socket helper functions.
+#include "ax25_pad.h"		// for AX25_MAX_PACKET_LEN
+#include "dlq.h"		// received packet queue
+
+#include "nettnc.h"
+
+
+
+void hex_dump (unsigned char *p, int len);
+
+
+// TODO: define macros in common locaation to hide platform specifics.
+
+#if __WIN32__
+#define THREAD_F unsigned __stdcall
+#else 
+#define THREAD_F void *
+#endif
+
+#if __WIN32__
+static HANDLE nettnc_listen_th[MAX_TOTAL_CHANS];
+static THREAD_F nettnc_listen_thread (void *arg);
+#else
+static pthread_t nettnc_listen_tid[MAX_TOTAL_CHANS];
+static THREAD_F nettnc_listen_thread (void *arg);	
+#endif
+
+static void my_kiss_rec_byte (kiss_frame_t *kf, unsigned char b, int debug, int channel_override);
+
+int s_kiss_debug = 0;
+
+
+/*-------------------------------------------------------------------
+ *
+ * Name:        nettnc_init
+ *
+ * Purpose:      Attach to Network KISS TNC(s) for NCHANNEL config file item(s).
+ *
+ * Inputs:	pa              - Address of structure of type audio_s.
+ *
+ *		debug ? TBD
+ *
+ *
+ * Returns:	0 for success, -1 for failure.
+ *
+ * Description:	Called once at direwolf application start up time.
+ *		Calls nettnc_attach for each NCHANNEL configuration item.
+ *
+ *--------------------------------------------------------------------*/
+
+void nettnc_init (struct audio_s *pa)
+{
+	for (int i = 0; i < MAX_TOTAL_CHANS; i++) {
+
+	  if (pa->chan_medium[i] == MEDIUM_NETTNC) {
+	    text_color_set(DW_COLOR_DEBUG);
+	    dw_printf ("Channel %d: Network TNC %s %d\n", i, pa->nettnc_addr[i], pa->nettnc_port[i]);
+	    int e = nettnc_attach (i, pa->nettnc_addr[i], pa->nettnc_port[i]);
+	    if (e < 0) {
+	      exit (1);
+	    }
+	  }
+	}
+
+}  // end nettnc_init
+
+
+
+/*-------------------------------------------------------------------
+ *
+ * Name:        nettnc_attach
+ *
+ * Purpose:      Attach to one Network KISS TNC.
+ *
+ * Inputs:	chan	- channel number from NCHANNEL configuration.
+ *
+ *		host	- Host name or IP address.  Often "localhost".
+ *
+ *		port	- TCP port number.  Typically 8001.
+ *
+ *		init_func - Call this function after establishing communication //
+ *			with the TNC.  We put it here, so that it can be done//
+ *			again automatically if the TNC disappears and we//
+ *			reattach to it.//
+ *			It must return 0 for success.//
+ *			Can be NULL if not needed.//
+ *
+ * Returns:	0 for success, -1 for failure.
+ *
+ * Description:	This starts up a thread, for each socket, which listens to the socket and
+ *		dispatches the messages to the corresponding callback functions.
+ *		It will also attempt to re-establish communication with the
+ *		TNC if it goes away.
+ *
+ *--------------------------------------------------------------------*/
+
+static char s_tnc_host[MAX_TOTAL_CHANS][80];
+static char s_tnc_port[MAX_TOTAL_CHANS][20];
+static volatile int s_tnc_sock[MAX_TOTAL_CHANS];	// Socket handle or file descriptor. -1 for invalid.
+
+
+int nettnc_attach (int chan, char *host, int port)
+{
+	assert (chan >= 0 && chan < MAX_TOTAL_CHANS);
+
+	char tncaddr[DWSOCK_IPADDR_LEN];
+
+	char sport[20];		// need port as text string later.
+	snprintf (sport, sizeof(sport), "%d", port);
+
+	strlcpy (s_tnc_host[chan], host, sizeof(s_tnc_host[chan]));
+	strlcpy (s_tnc_port[chan], sport, sizeof(s_tnc_port[chan]));
+	s_tnc_sock[chan] = -1;
+
+	dwsock_init();
+
+	s_tnc_sock[chan] = dwsock_connect (s_tnc_host[chan], s_tnc_port[chan], "Network TNC", 0, 0, tncaddr);
+
+	if (s_tnc_sock[chan] == -1) {
+	  return (-1);
+	}
+
+
+/*
+ * Read frames from the network TNC.
+ * If the TNC disappears, try to reestablish communication.
+ */
+
+
+#if __WIN32__
+	nettnc_listen_th[chan] = (HANDLE)_beginthreadex (NULL, 0, nettnc_listen_thread, (void *)(ptrdiff_t)chan, 0, NULL);
+	if (nettnc_listen_th[chan] == NULL) {
+	  text_color_set(DW_COLOR_ERROR);
+	  dw_printf ("Internal error: Could not create remore TNC listening thread\n");
+	  return (-1);
+	}
+#else
+	int e = pthread_create (&nettnc_listen_tid[chan], NULL, nettnc_listen_thread, (void *)(ptrdiff_t)chan);
+	if (e != 0) {
+	  text_color_set(DW_COLOR_ERROR);
+	  perror("Internal error: Could not create network TNC listening thread");
+	  return (-1);
+	}
+#endif
+
+// TNC initialization if specified.
+
+//	if (s_tnc_init_func != NULL) {
+//	  e = (*s_tnc_init_func)();
+//	  return (e);
+//	}
+
+	return (0);
+
+}  // end nettnc_attach
+
+
+
+/*-------------------------------------------------------------------
+ *
+ * Name:        nettnc_listen_thread
+ *
+ * Purpose:     Listen for anything from TNC and process it.
+ *		Reconnect if something goes wrong and we got disconnected.
+ *
+ * Inputs:	arg			- Channel number.
+ *		s_tnc_host[chan]	- Host & port for re-connection.
+ *		s_tnc_port[chan]
+ *
+ * Outputs:	s_tnc_sock[chan] - File descriptor for communicating with TNC.
+ *				  Will be -1 if not connected.
+ *
+ *--------------------------------------------------------------------*/
+
+#if __WIN32__
+static unsigned __stdcall nettnc_listen_thread (void *arg)
+#else
+static void * nettnc_listen_thread (void *arg)	
+#endif	
+{
+	int chan = (int)(ptrdiff_t)arg;
+	assert (chan >= 0 && chan < MAX_TOTAL_CHANS);
+
+	kiss_frame_t kstate;	 // State machine to gather a KISS frame.
+	memset (&kstate, 0, sizeof(kstate));
+
+	char tncaddr[DWSOCK_IPADDR_LEN];	// IP address used by dwsock_connect.
+						// Useful when rotate addresses used.
+
+// Set up buffer for collecting a KISS frame.$CC exttnc.c
+
+	while (1) {
+/*
+ * Re-attach to TNC if not currently attached.
+ */
+	  if (s_tnc_sock[chan] == -1) {
+
+	    text_color_set(DW_COLOR_ERROR);
+	    // I'm using the term "attach" here, in an attempt to
+	    // avoid confusion with the AX.25 connect.
+	    dw_printf ("Attempting to reattach to network TNC...\n");
+
+	    s_tnc_sock[chan] = dwsock_connect (s_tnc_host[chan], s_tnc_port[chan], "Network TNC", 0, 0, tncaddr);
+
+	    if (s_tnc_sock[chan] != -1) {
+	      dw_printf ("Successfully reattached to network TNC.\n");
+	    }
+	  }
+	  else {
+#define NETTNCBUFSIZ 2048
+	    unsigned char buf[NETTNCBUFSIZ];
+	    int n = SOCK_RECV (s_tnc_sock[chan], (char *)buf, sizeof(buf));
+
+	    if (n == -1) {
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("Lost communication with network TNC. Will try to reattach.\n");
+	      dwsock_close (s_tnc_sock[chan]);
+	      s_tnc_sock[chan] = -1;
+	      SLEEP_SEC(5);
+	      continue;
+	    }
+
+#if 0
+	    text_color_set(DW_COLOR_DEBUG);
+	    dw_printf ("TEMP DEBUG:  %d bytes received from channel %d network TNC.\n", n, chan);
+#endif
+	    for (int j = 0; j < n; j++) {
+	      // Separate the byte stream into KISS frame(s) and make it
+	      // look like this came from a radio channel.
+	      my_kiss_rec_byte (&kstate, buf[j], s_kiss_debug, chan);
+	    }
+	  } // s_tnc_sock != -1
+	} // while (1)
+
+	return (0);	// unreachable but shutup warning.
+
+} // end nettnc_listen_thread
+
+
+
+/*-------------------------------------------------------------------
+ *
+ * Name:        my_kiss_rec_byte 
+ *
+ * Purpose:     Process one byte from a KISS network TNC.
+ *
+ * Inputs:	kf	- Current state of building a frame.
+ *		b	- A byte from the input stream.
+ *		debug	- Activates debug output.
+ *		channel_overide - Set incoming channel number to the NCHANNEL
+ *				number rather than the channel in the KISS frame.
+ *
+ * Outputs:	kf	- Current state is updated.
+ *
+ * Returns:	none.
+ *
+ * Description:	This is a simplified version of kiss_rec_byte used
+ *		for talking to KISS client applications.  It already has
+ *		too many special cases and I don't want to make it worse.
+ *		This also needs to make the packet look like it came from
+ *		a radio channel, not from a client app.
+ *
+ *-----------------------------------------------------------------*/
+
+static void my_kiss_rec_byte (kiss_frame_t *kf, unsigned char b, int debug, int channel_override)
+{
+
+	//dw_printf ("my_kiss_rec_byte ( %c %02x ) \n", b, b);
+	
+	switch (kf->state) {
+	 
+  	  case KS_SEARCHING:		/* Searching for starting FEND. */
+	  default:
+
+	    if (b == FEND) {
+	      
+	      /* Start of frame.  */
+	      
+	      kf->kiss_len = 0;
+	      kf->kiss_msg[kf->kiss_len++] = b;
+	      kf->state = KS_COLLECTING;
+	      return;
+	    }
+	    return;
+	    break;
+
+	  case KS_COLLECTING:		/* Frame collection in progress. */
+
+     
+	    if (b == FEND) {
+	      
+	      unsigned char unwrapped[AX25_MAX_PACKET_LEN];
+	      int ulen;
+
+	      /* End of frame. */
+
+	      if (kf->kiss_len == 0) {
+		/* Empty frame.  Starting a new one. */
+	        kf->kiss_msg[kf->kiss_len++] = b;
+	        return;
+	      }
+	      if (kf->kiss_len == 1 && kf->kiss_msg[0] == FEND) {
+		/* Empty frame.  Just go on collecting. */
+	        return;
+	      }
+
+	      kf->kiss_msg[kf->kiss_len++] = b;
+	      if (debug) {
+		/* As received over the wire from network TNC. */
+		// May include escapted characters.  What about FEND?
+// FIXME: make it say Network TNC.
+	        kiss_debug_print (FROM_CLIENT, NULL, kf->kiss_msg, kf->kiss_len);
+	      }
+
+	      ulen = kiss_unwrap (kf->kiss_msg, kf->kiss_len, unwrapped);
+
+	      if (debug >= 2) {
+	        /* Append CRC to this and it goes out over the radio. */
+	        text_color_set(DW_COLOR_DEBUG);
+	        dw_printf ("\n");
+	        dw_printf ("Frame content after removing KISS framing and any escapes:\n");
+	        /* Don't include the "type" indicator. */
+		/* It contains the radio channel and type should always be 0 here. */
+	        hex_dump (unwrapped+1, ulen-1);
+	      }
+
+	      // Convert to packet object and send to received packet queue.
+	      // Note that we use channel associated with the network TNC, not channel in KISS frame.
+
+	      int subchan = -3;
+	      int slice = 0;
+	      alevel_t alevel;  
+	      memset(&alevel, 0, sizeof(alevel));
+	      packet_t pp = ax25_from_frame (unwrapped+1, ulen-1, alevel);
+	      if (pp != NULL) {
+	        fec_type_t fec_type = fec_type_none;
+	        retry_t retries;
+	        memset (&retries, 0, sizeof(retries));
+	        char spectrum[] = "Network TNC";
+	        dlq_rec_frame (channel_override, subchan, slice, pp, alevel, fec_type, retries, spectrum);
+	      }
+	      else {
+	   	text_color_set(DW_COLOR_ERROR);
+	        dw_printf ("Failed to create packet object for KISS frame from channel %d network TNC.\n", channel_override);
+	      }
+     
+	      kf->state = KS_SEARCHING;
+	      return;
+	    }
+
+	    if (kf->kiss_len < MAX_KISS_LEN) {
+	      kf->kiss_msg[kf->kiss_len++] = b;
+	    }
+	    else {	    
+	      text_color_set(DW_COLOR_ERROR);
+	      dw_printf ("KISS frame from network TNC exceeded maximum length.\n");
+	    }	      
+	    return;
+	    break;
+	}
+	
+	return;	/* unreachable but suppress compiler warning. */
+
+} /* end my_kiss_rec_byte */   
+	      	    
+
+
+
+
+
+
+
+
+/*-------------------------------------------------------------------
+ *
+ * Name:	nettnc_send_packet
+ *
+ * Purpose:	Send packet to a KISS network TNC.
+ *
+ * Inputs:	chan	- Channel number from NCHANNEL configuration.
+ *		pp	- Packet object.
+ *		b	- A byte from the input stream.
+ *
+ * Outputs:	Packet is converted to KISS and send to network TNC.
+ *
+ * Returns:	none.
+ *
+ * Description:	This does not free the packet object; caller is responsible.
+ *
+ *-----------------------------------------------------------------*/
+
+void nettnc_send_packet (int chan, packet_t pp)
+{
+
+// First, get the on-air frame format from packet object.
+// Prepend 0 byte for KISS command and channel.
+
+	unsigned char frame_buff[AX25_MAX_PACKET_LEN + 2];	// One byte for channel/command,
+							// followed by the AX.25 on-air format frame.
+	frame_buff[0] = 0;	// For now, set channel to 0.
+
+	unsigned char *fbuf = ax25_get_frame_data_ptr (pp);
+	int flen = ax25_get_frame_len (pp); 
+
+	memcpy (frame_buff+1, fbuf, flen);
+
+// Next, encapsulate into KISS frame with surrounding FENDs and any escapes.
+
+	unsigned char kiss_buff[2 * AX25_MAX_PACKET_LEN];
+	int kiss_len = kiss_encapsulate (frame_buff, flen+1, kiss_buff);
+
+#if __WIN32__	
+	int err = SOCK_SEND(s_tnc_sock[chan], (char*)kiss_buff, kiss_len);
+	if (err == SOCKET_ERROR) {
+	  text_color_set(DW_COLOR_ERROR);
+	  dw_printf ("\nError %d sending packet to KISS Network TNC for channel %d.  Closing connection.\n\n", WSAGetLastError(), chan);
+	  closesocket (s_tnc_sock[chan]);
+	  s_tnc_sock[chan] = -1;
+	}
+#else
+	int err = SOCK_SEND (kps->client_sock[chan], kiss_buff, kiss_len);
+	if (err <= 0) {
+	  text_color_set(DW_COLOR_ERROR);
+	  dw_printf ("\nError %d sending packet to KISS Network TNC for channel %d.  Closing connection.\n\n", err, chan);
+	  close (s_tnc_sock[chan]);
+	  s_tnc_sock[chan] = -1;
+	}
+#endif
+	
+	// Do not free packet object;  caller will take care of it.
+
+} /* end nettnc_send_packet */
+
diff --git a/src/nettnc.h b/src/nettnc.h
new file mode 100644
index 0000000..d8a10f4
--- /dev/null
+++ b/src/nettnc.h
@@ -0,0 +1,7 @@
+
+
+void nettnc_init (struct audio_s *pa);
+
+int nettnc_attach (int chan, char *host, int port);
+
+void nettnc_send_packet (int chan, packet_t pp);
\ No newline at end of file