hodu/client.go

package main


//import "bufio"
import "context"
import "crypto/tls"
import "crypto/x509"
import "encoding/json"
import "errors"
import "fmt"
import "io"
import "log"
import "net"
import "net/http"
import "os"
import "os/signal"
import "sync"
import "sync/atomic"
import "syscall"
import "time"

//import "github.com/google/uuid"
import "google.golang.org/grpc"
import "google.golang.org/grpc/credentials/insecure"

const PTC_LIMIT = 8192

type PacketStreamClient grpc.BidiStreamingClient[Packet, Packet]

type ServerConnMap = map[net.Addr]*ServerConn
type ClientPeerConnMap = map[uint32]*ClientPeerConn
type ClientRouteMap = map[uint32]*ClientRoute
type ClientPeerCancelFuncMap = map[uint32]context.CancelFunc

// --------------------------------------------------------------------
type ClientConfig struct {
	server_addr string
	peer_addrs []string
}

type Client struct {
	ctx         context.Context
	ctx_cancel  context.CancelFunc
	tlscfg     *tls.Config

	ctl        *http.Server // control server

	cts_mtx     sync.Mutex
	cts_map     ServerConnMap

	wg          sync.WaitGroup
	stop_req    atomic.Bool
	stop_chan   chan bool
}

type ClientPeerConn struct {
	route *ClientRoute
	conn_id uint32
	conn *net.TCPConn
	remot_conn_id uint32

	addr     string // peer address

	stop_chan chan bool
	stop_req atomic.Bool
	server_peer_eof atomic.Bool
}

// client connection to server
type ServerConn struct {
	cli      *Client
	cfg      *ClientConfig
	saddr    *net.TCPAddr // server address that is connected to

	conn     *grpc.ClientConn // grpc connection to the server
	hdc       HoduClient
	psc      *GuardedPacketStreamClient // guarded grpc stream

	s_seed    Seed
	c_seed    Seed

	route_mtx sync.Mutex
	route_map ClientRouteMap
	route_wg  sync.WaitGroup

	stop_req  atomic.Bool
	stop_chan chan bool
}

type ClientRoute struct {
	cts *ServerConn
	id uint32
	peer_addr *net.TCPAddr
	proto ROUTE_PROTO

	ptc_mtx        sync.Mutex
	ptc_map        ClientPeerConnMap
	ptc_cancel_map ClientPeerCancelFuncMap
	//ptc_limit      int
	//ptc_last_id    uint32
	ptc_wg sync.WaitGroup

	stop_req atomic.Bool
	stop_chan chan bool
}

type ClientCtlParamServer struct {
	ServerAddr string  `json:"server-addr"`
	PeerAddrs []string `json:"peer-addrs"`
}

type GuardedPacketStreamClient struct {
	mtx sync.Mutex
	//psc Hodu_PacketStreamClient
	Hodu_PacketStreamClient
}

// ------------------------------------

func (g *GuardedPacketStreamClient) Send(data *Packet) error {
	g.mtx.Lock()
	defer g.mtx.Unlock()
	//return g.psc.Send(data)
	return g.Hodu_PacketStreamClient.Send(data)
}

/*func (g *GuardedPacketStreamClient) Recv() (*Packet, error) {
	return g.psc.Recv()
}

func (g *GuardedPacketStreamClient) Context() context.Context {
	return g.psc.Context()
}*/

// --------------------------------------------------------------------
func NewClientRoute(cts *ServerConn, id uint32, addr *net.TCPAddr, proto ROUTE_PROTO) *ClientRoute {
	var r ClientRoute

	r.cts = cts
	r.id = id
	//r.ptc_limit = PTC_LIMIT
	r.ptc_map = make(ClientPeerConnMap)
	r.ptc_cancel_map = make(ClientPeerCancelFuncMap)
	//r.ptc_last_id = 0
	r.proto = proto
	r.peer_addr = addr
	r.stop_req.Store(false)
	r.stop_chan = make(chan bool, 1)

	return &r;
}

func (r *ClientRoute) RunTask(wg *sync.WaitGroup) {
	// this task on the route object isn't actually necessary.
	// most useful works are triggered by ReportEvent() and done by ConnectToPeer()
	defer wg.Done()

main_loop:
	for {
		select {
			case <- r.stop_chan:
				break main_loop
		}
	}

	r.ptc_wg.Wait() // wait for all peer tasks are finished
fmt.Printf ("*** End fo Client Roue Task\n")
}

func (r *ClientRoute) ReqStop() {
	if r.stop_req.CompareAndSwap(false, true) {
		var ptc *ClientPeerConn
		for _, ptc = range r.ptc_map {
			ptc.ReqStop()
		}

		r.stop_chan <- true
	}
fmt.Printf ("*** Sent stop request to Route..\n");
}

func (r* ClientRoute) ConnectToPeer(pts_id uint32, wg *sync.WaitGroup) {
	var err error
	var conn net.Conn
	var real_conn *net.TCPConn
	var ptc *ClientPeerConn
	var d net.Dialer
	var ctx context.Context
	var cancel context.CancelFunc
	var ok bool

	defer wg.Done()

// TODO: make timeuot value configurable
// TODO: fire the cancellation function upon stop request???
	ctx, cancel = context.WithTimeout(r.cts.cli.ctx, 10 * time.Second)
	r.ptc_mtx.Lock()
	r.ptc_cancel_map[pts_id] = cancel
	r.ptc_mtx.Unlock()

	d.LocalAddr = nil // TOOD: use this if local address is specified
	conn, err = d.DialContext(ctx, "tcp", r.peer_addr.String());

	r.ptc_mtx.Lock()
	delete(r.ptc_cancel_map, pts_id)
	r.ptc_mtx.Unlock()

	if err != nil {
// TODO: make send peer started failure mesage?
		fmt.Printf ("failed to connect to %s - %s\n", r.peer_addr.String(), err.Error())
		goto peer_aborted
	}

	real_conn, ok = conn.(*net.TCPConn)
	if !ok {
		fmt.Printf("not tcp connection - %s\n", err.Error())
		goto peer_aborted
	}

	ptc, err = r.AddNewClientPeerConn(real_conn, pts_id)
	if err != nil {
		// TODO: logging
// TODO: make send peer started failure mesage?
		fmt.Printf("YYYYYYYY - %s\n", err.Error())
		goto peer_aborted
	}
	fmt.Printf("STARTED NEW SERVER PEER STAK\n")
	err = r.cts.psc.Send(MakePeerStartedPacket(r.id, ptc.conn_id))
	if err != nil {
		fmt.Printf("CLOSING NEW SERVER PEER STAK - %s\n", err.Error())
		goto peer_aborted
	}

	wg.Add(1)
	go ptc.RunTask(wg)
	return

peer_aborted:
	if conn != nil {
		conn.Close()
		err = r.cts.psc.Send(MakePeerAbortedPacket(r.id, ptc.conn_id))
		if err != nil {
			// TODO: logging
		}
	}
}

func (r* ClientRoute) DisconnectFromPeer(pts_id uint32) error {
	var ptc *ClientPeerConn
	var cancel context.CancelFunc
	var ok bool

	r.ptc_mtx.Lock()
	cancel, ok = r.ptc_cancel_map[pts_id]
	if ok {
fmt.Printf ("~~~~~~~~~~~~~~~~ cancelling.....\n")
		cancel()
	}

	ptc, ok = r.ptc_map[pts_id]
	if !ok {
		r.ptc_mtx.Unlock()
		return fmt.Errorf("non-existent connection id - %u", pts_id)
	}
	r.ptc_mtx.Unlock()

	ptc.ReqStop()
	return nil
}

func (r* ClientRoute) CloseWriteToPeer(pts_id uint32) error {
	var ptc *ClientPeerConn
	var ok bool

	r.ptc_mtx.Lock()
	ptc, ok = r.ptc_map[pts_id]
	if !ok {
		r.ptc_mtx.Unlock()
		return fmt.Errorf("non-existent connection id - %u", pts_id)
	}
	r.ptc_mtx.Unlock()

	ptc.CloseWrite()
	return nil
}


func (r* ClientRoute) ReportEvent (pts_id uint32, event_type PACKET_KIND, event_data []byte) error {
	var err error

	switch event_type {
		case PACKET_KIND_PEER_STARTED:
fmt.Printf ("GOT PEER STARTD . CONENCT TO CLIENT_SIDE PEER\n")
			r.ptc_wg.Add(1)
			go r.ConnectToPeer(pts_id, &r.ptc_wg)

		case PACKET_KIND_PEER_ABORTED:
			fallthrough
		case PACKET_KIND_PEER_STOPPED:
fmt.Printf ("GOT PEER STOPPED . DISCONNECTION FROM CLIENT_SIDE PEER\n")
			err = r.DisconnectFromPeer(pts_id)
			if err != nil {
				// TODO:
			}

		case PACKET_KIND_PEER_EOF:
fmt.Printf ("GOT PEER EOF. REMEMBER EOF\n")
			err = r.CloseWriteToPeer(pts_id)
			if err != nil {
				// TODO:
			}

		case PACKET_KIND_PEER_DATA:
			var ptc *ClientPeerConn
			var ok bool
			var err error
			ptc, ok = r.ptc_map[pts_id]
			if ok {
				_, err = ptc.conn.Write(event_data)
				return err
			} else {

			}

		// TODO: other types
	}

	return nil
}

// --------------------------------------------------------------------
func NewServerConn(c *Client, addr *net.TCPAddr, cfg *ClientConfig) *ServerConn {
	var cts ServerConn

	cts.cli = c
	cts.route_map = make(ClientRouteMap)
	cts.saddr = addr
	cts.cfg = cfg
	cts.stop_req.Store(false)
	cts.stop_chan = make(chan bool, 1)

	// the actual connection to the server is established in the main task function
	// The cts.conn, cts.hdc, cts.psc fields are left unassigned here.

	return &cts
}

func (cts *ServerConn) AddNewClientRoute(route_id uint32, addr *net.TCPAddr, proto ROUTE_PROTO) (*ClientRoute, error) {
	var r *ClientRoute

	cts.route_mtx.Lock()
	if cts.route_map[route_id] != nil {
		cts.route_mtx.Unlock()
		return nil, fmt.Errorf ("existent route id - %d", route_id)
	}
	r = NewClientRoute(cts, route_id, addr, proto)
	cts.route_map[route_id] = r
	cts.route_mtx.Unlock()

fmt.Printf ("added client route.... %d -> %d\n", route_id, len(cts.route_map))
	cts.route_wg.Add(1)
	go r.RunTask(&cts.route_wg)
	return r, nil
}

func (cts *ServerConn) RemoveClientRoute (route_id uint32) error {
	var r *ClientRoute
	var ok bool

	cts.route_mtx.Lock()
	r, ok = cts.route_map[route_id]
	if (!ok) {
		cts.route_mtx.Unlock()
		return fmt.Errorf ("non-existent route id - %d", route_id)
	}
	delete(cts.route_map, route_id)
	cts.route_mtx.Unlock()

	r.ReqStop() // TODO: make this unblocking or blocking?
	return nil;
}

func (cts *ServerConn) RemoveClientRoutes () {
	var r *ClientRoute
	var id uint32

	cts.route_mtx.Lock()
	for _, r = range cts.route_map {
		r.ReqStop()
	}

	for id, r = range cts.route_map {
		delete(cts.route_map, id)
	}

	cts.route_map = make(ClientRouteMap)
	cts.route_mtx.Unlock()
}

func (cts *ServerConn) AddClientRoutes (peer_addrs []string) error {
	var i int
	var v string
	var addr *net.TCPAddr
	var proto ROUTE_PROTO
	var r *ClientRoute
	var err error

	for i, v = range peer_addrs {
		addr, err = net.ResolveTCPAddr(NET_TYPE_TCP, v)
		if err != nil {
			return fmt.Errorf("unable to resovle %s - %s", v, err.Error())
		}

		if addr.IP.To4() != nil {
			proto = ROUTE_PROTO_TCP4
		} else {
			proto = ROUTE_PROTO_TCP6
		}

		_, err = cts.AddNewClientRoute(uint32(i), addr, proto)
		if err != nil {
			return fmt.Errorf("unable to add client route for %s - %s", addr, err.Error())
		}
	}

	for _, r = range cts.route_map  {
		err = cts.psc.Send(MakeRouteStartPacket(r.id, r.proto, addr.String()))
		if err != nil {
			return fmt.Errorf("unable to send route-start packet - %s", err.Error())
		}
	}

	return nil;
}

func (cts *ServerConn) ReqStop() {
	if cts.stop_req.CompareAndSwap(false, true) {
		var r *ClientRoute

		cts.route_mtx.Lock()
		for _, r = range cts.route_map {
			r.ReqStop()
		}
		cts.route_mtx.Unlock()

		// TODO: notify the server.. send term command???
		cts.stop_chan <- true
	}
fmt.Printf ("*** Sent stop request to ServerConn..\n");
}

func (cts *ServerConn) RunTask(wg *sync.WaitGroup) {
	var conn *grpc.ClientConn = nil
	var hdc HoduClient
	var psc PacketStreamClient
	var slpctx context.Context
	var c_seed Seed
	var s_seed *Seed
	var err error

	defer wg.Done() // arrange to call at the end of this function

// TODO: HANDLE connection timeout..
	//	ctx, _/*cancel*/ := context.WithTimeout(context.Background(), time.Second)
start_over:
fmt.Printf ("Connecting GRPC to [%s]\n", cts.saddr.String())
	conn, err = grpc.NewClient(cts.saddr.String(), grpc.WithTransportCredentials(insecure.NewCredentials()))
	if err != nil {
	// TODO: logging
		fmt.Printf("ERROR: unable to make grpc client to %s - %s\n", cts.cfg.server_addr, err.Error())
		goto reconnect_to_server
	}

	hdc = NewHoduClient(conn)

	// seed exchange is for furture expansion of the protocol
	// there is nothing to do much about it for now.
	c_seed.Version = HODU_VERSION
	c_seed.Flags = 0
	s_seed, err = hdc.GetSeed(cts.cli.ctx, &c_seed)
	if err != nil {
		fmt.Printf("ERROR: unable to get seed from %s - %s\n", cts.cfg.server_addr, err.Error())
		goto reconnect_to_server
	}
	cts.s_seed = *s_seed
	cts.c_seed = c_seed

	psc, err = hdc.PacketStream(cts.cli.ctx)
	if err != nil {
		fmt.Printf ("ERROR: unable to get grpc packet stream - %s\n", err.Error())
		goto reconnect_to_server
	}

	cts.conn = conn
	cts.hdc = hdc
	//cts.psc = &GuardedPacketStreamClient{psc: psc}
	cts.psc = &GuardedPacketStreamClient{Hodu_PacketStreamClient: psc}

	// the connection structure to a server is ready.
	// let's add routes to the client-side peers.
	err = cts.AddClientRoutes(cts.cfg.peer_addrs)
	if err != nil {
		fmt.Printf ("ERROR: unable to add routes to client-side peers - %s\n", err.Error())
		goto done
	}
fmt.Printf("[%v]\n", cts.route_map)

	for {
		var pkt *Packet

		select {
			case <-cts.cli.ctx.Done():
				fmt.Printf("context doine... error - %s\n", cts.cli.ctx.Err().Error())
				goto done

			case <-cts.stop_chan:
				goto done

			default:
				// no other case is ready. run the code below select.
				// without the default case, the select construct would block
		}

		pkt, err = psc.Recv()
		if errors.Is(err, io.EOF) {
			fmt.Printf("server disconnected\n")
			goto reconnect_to_server
		}
		if err != nil {
			fmt.Printf("server receive error - %s\n", err.Error())
			goto reconnect_to_server
		}

		switch pkt.Kind {
			case PACKET_KIND_ROUTE_STARTED:
				// the server side managed to set up the route the client requested
				var x *Packet_Route
				var ok bool
				x, ok = pkt.U.(*Packet_Route)
				if ok {
	fmt.Printf ("SERVER LISTENING ON %s\n", x.Route.AddrStr);
					err = cts.ReportEvent(x.Route.RouteId, 0, pkt.Kind, nil)
					if err != nil {
						// TODO:
					} else {
						// TODO:
					}
				} else {
					// TODO: send invalid request... or simply keep quiet?
				}

			case PACKET_KIND_ROUTE_STOPPED:
				var x *Packet_Route
				var ok bool
				x, ok = pkt.U.(*Packet_Route)
				if ok {
					err = cts.ReportEvent(x.Route.RouteId, 0, pkt.Kind, nil)
					if err != nil {
						// TODO:
					} else {
						// TODO:
					}
				} else {
					// TODO: send invalid request... or simply keep quiet?
				}

			case PACKET_KIND_PEER_STARTED:
				// the connection from the client to a peer has been established
				var x *Packet_Peer
				var ok bool
				x, ok = pkt.U.(*Packet_Peer)
				if ok {
					err = cts.ReportEvent(x.Peer.RouteId, x.Peer.PeerId, PACKET_KIND_PEER_STARTED, nil)
					if err != nil {
						// TODO:
					} else {
						// TODO:
					}
				} else {
					// TODO
				}

			case PACKET_KIND_PEER_STOPPED:
				// the connection from the client to a peer has been established
				var x *Packet_Peer
				var ok bool
				x, ok = pkt.U.(*Packet_Peer)
				if ok {
					err = cts.ReportEvent(x.Peer.RouteId, x.Peer.PeerId, PACKET_KIND_PEER_STOPPED, nil)
					if err != nil {
						// TODO:
					} else {
						// TODO:
					}
				} else {
					// TODO
				}

			case PACKET_KIND_PEER_EOF:
				var x *Packet_Peer
				var ok bool
				x, ok = pkt.U.(*Packet_Peer)
				if ok {
					err = cts.ReportEvent(x.Peer.RouteId, x.Peer.PeerId, PACKET_KIND_PEER_EOF, nil)
					if err != nil {
						// TODO:
					} else {
						// TODO:
					}
				} else {
					// TODO
				}

			case PACKET_KIND_PEER_DATA:
				// the connection from the client to a peer has been established
	fmt.Printf ("**** GOT PEER DATA\n")
				var x *Packet_Data
				var ok bool
				x, ok = pkt.U.(*Packet_Data)
				if ok {
					err = cts.ReportEvent(x.Data.RouteId, x.Data.PeerId, PACKET_KIND_PEER_DATA, x.Data.Data)
					if err != nil {
		fmt.Printf ("failed to report event - %s\n", err.Error())
						// TODO:
					} else {
						// TODO:
					}
				} else {
					// TODO
				}
		}
	}

done:
fmt.Printf ("^^^^^^^^^^^^^^^^^^^^ Server Coon RunTask ending...\n")
	if conn != nil {
		conn.Close()
		// TODO: need to reset c.sc, c.sg, c.psc to nil?
		//       for this we need to ensure that everyone is ending
	}
	cts.RemoveClientRoutes()
	cts.route_wg.Wait() // wait until all route tasks are finished
	return

reconnect_to_server:
	if conn != nil {
		conn.Close()
		// TODO: need to reset c.sc, c.sg, c.psc to nil?
		//       for this we need to ensure that everyone is ending
	}
	cts.RemoveClientRoutes()
	slpctx, _ = context.WithTimeout(cts.cli.ctx, 3 * time.Second)
	select {
		case <-cts.cli.ctx.Done():
			fmt.Printf("context doine... error - %s\n", cts.cli.ctx.Err().Error())
			goto done
		case <-cts.stop_chan:
			goto done
		case <- slpctx.Done():
			// do nothing
	}
	goto start_over
}

func (cts *ServerConn) ReportEvent (route_id uint32, pts_id uint32, event_type PACKET_KIND, event_data []byte) error {
	var r *ClientRoute
	var ok bool

	cts.route_mtx.Lock()
	r, ok = cts.route_map[route_id]
	if (!ok) {
		cts.route_mtx.Unlock()
		return fmt.Errorf ("non-existent route id - %d", route_id)
	}
	cts.route_mtx.Unlock()

	return r.ReportEvent(pts_id, event_type, event_data)
}
// --------------------------------------------------------------------

func (r *ClientRoute) AddNewClientPeerConn (c *net.TCPConn, pts_id uint32) (*ClientPeerConn, error) {
	var ptc *ClientPeerConn
	//var ok bool
	//var start_id uint32

	r.ptc_mtx.Lock()
	defer r.ptc_mtx.Unlock()

/*
	if len(r.ptc_map) >= r.ptc_limit {
		return nil, fmt.Errorf("peer-to-client connection table full")
	}

	start_id = r.ptc_last_id
	for {
		_, ok = r.ptc_map[r.ptc_last_id]
		if !ok {
			break
		}
		r.ptc_last_id++
		if r.ptc_last_id == start_id {
			// unlikely to happen but it cycled through the whole range.
			return nil, fmt.Errorf("failed to assign peer-to-table connection id")
		}
	}

	ptc = NewClientPeerConn(r, c, r.ptc_last_id)
*/
	ptc = NewClientPeerConn(r, c, pts_id)
	r.ptc_map[ptc.conn_id] = ptc
	//r.ptc_last_id++

	return ptc, nil
}

// --------------------------------------------------------------------


func NewClient(ctx context.Context, listen_on string, tlscfg *tls.Config) *Client {
	var c Client

	c.ctx, c.ctx_cancel = context.WithCancel(ctx)
	c.tlscfg = tlscfg
	c.cts_map = make(ServerConnMap) // TODO: make it configurable...
	c.stop_req.Store(false)
	c.stop_chan = make(chan bool, 1)

	c.ctl = &http.Server{
		Addr: listen_on,
		Handler: &c,
	}

	return &c
}

func (c *Client) AddNewServerConn(addr *net.TCPAddr, cfg *ClientConfig) (*ServerConn, error) {
	var cts *ServerConn
	var ok bool

	cts = NewServerConn(c, addr, cfg)

	c.cts_mtx.Lock()
	defer c.cts_mtx.Unlock()

	_, ok = c.cts_map[addr]
	if ok {
		return nil, fmt.Errorf("existing server - %s", addr.String())
	}

	c.cts_map[addr] = cts;
fmt.Printf ("ADD total servers %d\n", len(c.cts_map));
	return cts, nil
}

func (c *Client) RemoveServerConn(cts *ServerConn) {
	c.cts_mtx.Lock()
	delete(c.cts_map, cts.saddr)
fmt.Printf ("REMOVE total servers %d\n", len(c.cts_map));
	c.cts_mtx.Unlock()
}

func (c *Client) ReqStop() {
	if c.stop_req.CompareAndSwap(false, true) {
		var cts *ServerConn

		c.ctl.Shutdown(c.ctx) // to break c.ctl.ListenAndServe()

		for _, cts = range c.cts_map {
			cts.ReqStop()
		}

		// TODO: notify the server.. send term command???
		c.stop_chan <- true
		c.ctx_cancel()
	}
fmt.Printf ("*** Sent stop request to client..\n");
}

func (c *Client) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	var err error

	// command handler for the control channel
	if req.URL.String() == "/servers" {
		switch req.Method {
			case http.MethodGet:
				goto bad_request // TODO:

			case http.MethodPost:
				var s ClientCtlParamServer
				var cc ClientConfig
				err = json.NewDecoder(req.Body).Decode(&s)
				if err != nil {
		fmt.Printf ("failed to decode body - %s\n", err.Error())
					goto bad_request
				}
				cc.server_addr = s.ServerAddr
				cc.peer_addrs = s.PeerAddrs
				c.RunService(&cc)
				w.WriteHeader(http.StatusCreated)

			case http.MethodPut:
				goto bad_request // TODO:

			case http.MethodDelete:
				var cts *ServerConn
				for _, cts = range c.cts_map {
					cts.ReqStop()
				}
		}
	} else {
		goto bad_request
	}
	fmt.Printf ("[%s][%s][%s]\n", req.RequestURI, req.URL.String(), req.Method)
	return

bad_request:
	w.WriteHeader(http.StatusBadRequest)
	return
}

/*
 *                       POST                 GET            PUT            DELETE
 * /servers -     create new server     list all servers    bulk update     delete all servers
 * /servers/1 -        X             get server 1 details  update server 1  delete server 1
 * /servers/1/xxx -
 */
func (c *Client) RunCtlTask(wg *sync.WaitGroup) {
	var err error

	defer wg.Done()

	err = c.ctl.ListenAndServe()
	if !errors.Is(err, http.ErrServerClosed) {
		fmt.Printf ("------------http server error - %s\n", err.Error())
	} else {
		fmt.Printf ("********* http server ended\n")
	}
}

// naming convention:
//   RunService - returns after having executed another go routine
//   RunTask - supposed to be detached as a go routine
func (c *Client) RunService(cfg *ClientConfig) {
	var saddr *net.TCPAddr
	var cts *ServerConn
	var err error

	if len(cfg.peer_addrs) < 0 || len(cfg.peer_addrs) > int(^uint16(0)) { // TODO: change this check... not really right...
		fmt.Printf("no peer addresses or too many peer addresses")
		return
	}

	saddr, err = net.ResolveTCPAddr(NET_TYPE_TCP, cfg.server_addr)
	if err != nil {
		fmt.Printf("unable to resolve %s - %s", cfg.server_addr, err.Error())
		return
	}

	cts, err = c.AddNewServerConn(saddr, cfg)
	if err != nil {
		fmt.Printf("unable to add server connection structure to %s - %s", cfg.server_addr, err.Error())
		return
	}

	c.wg.Add(1)
	go cts.RunTask(&c.wg)
}

func (c *Client) WaitForTermination() {

fmt.Printf ("Waiting for task top stop\n")
// waiting for tasks to stop
	c.wg.Wait()
fmt.Printf ("XXXXXXXXXXXX Waiting for task top stop\n")

	// TOOD: find a better way to stop the signal handling loop.
	//       above all the signal handler must not be with a single client,
	//       but with the whole app.
	syscall.Kill(syscall.Getpid(), syscall.SIGTERM) // TODO: find a better to terminate the signal handler...
}

// --------------------------------------------------------------------

func (c *Client) handle_os_signals() {
	var sighup_chan  chan os.Signal
	var sigterm_chan chan os.Signal
	var sig          os.Signal

	defer c.wg.Done()

	sighup_chan = make(chan os.Signal, 1)
	sigterm_chan = make(chan os.Signal, 1)

	signal.Notify(sighup_chan, syscall.SIGHUP)
	signal.Notify(sigterm_chan, syscall.SIGTERM, os.Interrupt)

chan_loop:
	for {
		select {
		case <-sighup_chan:
			// TODO:
			//s.RefreshConfig()
		case sig = <-sigterm_chan:
			// TODO: get timeout value from config
			//c.Shutdown(fmt.Sprintf("termination by signal %s", sig), 3*time.Second)
			c.ReqStop()
			//log.Debugf("termination by signal %s", sig)
			fmt.Printf("termination by signal %s\n", sig)
			break chan_loop
		}
	}
fmt.Printf("end of signal handler\n")
}

// --------------------------------------------------------------------

const rootCert = `-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
`

func client_main(listen_on string, server_addr string, peer_addrs []string) error {
	var c *Client
	var cert_pool *x509.CertPool
	var tlscfg *tls.Config
	var cc ClientConfig

	cert_pool = x509.NewCertPool()
	ok := cert_pool.AppendCertsFromPEM([]byte(rootCert))
	if !ok {
		log.Fatal("failed to parse root certificate")
	}
	tlscfg = &tls.Config{
		RootCAs: cert_pool,
		ServerName: "localhost",
		InsecureSkipVerify: true,
	}

	c = NewClient(context.Background(), listen_on, tlscfg)

	c.wg.Add(1)
	go c.handle_os_signals()

	c.wg.Add(1)
	go c.RunCtlTask(&c.wg) // control channel task

	cc.server_addr = server_addr
	cc.peer_addrs = peer_addrs
	c.RunService(&cc)

	c.WaitForTermination()

	return nil
}