server.py

#!/usr/bin/python3

import os
import threading
import gettext
import logging
import time
import re
from concurrent import futures
import time
import ipaddress
import urllib

from gi.repository import GObject, GLib

import grpc
import warp_pb2
import warp_pb2_grpc
from google import protobuf

import config
import auth
import interceptors
import networkmonitor
import remote
import remote_registration
import prefs
import util
import misc
import transfers
from ops import ReceiveOp, TextMessageOp
from util import TransferDirection, OpStatus, RemoteStatus, RemoteFeatures

import zeroconf
from zeroconf import ServiceInfo, Zeroconf, ServiceBrowser, IPVersion

_ = gettext.gettext

void = warp_pb2.VoidType()

SERVICE_TYPE = "_warpinator._tcp.local."

SERVER_FEATURES = RemoteFeatures.TEXT_MESSAGES

# server (this is on a separate thread from the ui, grpc isn't compatible with
# gmainloop)
class Server(threading.Thread, warp_pb2_grpc.WarpServicer, GObject.Object):
    __gsignals__ = {
        "remote-machine-added": (GObject.SignalFlags.RUN_LAST, None, (object,)),
        "remote-machine-removed": (GObject.SignalFlags.RUN_LAST, None, (object,)),
        "remote-machine-ops-changed": (GObject.SignalFlags.RUN_LAST, None, (str,)),
        "local-info-changed": (GObject.SignalFlags.RUN_LAST, None, (str,)),
        "server-started": (GObject.SignalFlags.RUN_LAST, None, ()),
        "shutdown-complete": (GObject.SignalFlags.RUN_LAST, None, ()),
        "manual-connect-result": (GObject.SignalFlags.RUN_LAST, None, (bool, bool, str)),
    }
    def __init__(self, ip_info, port, auth_port):
        threading.Thread.__init__(self, name="server-thread")
        super(Server, self).__init__()
        GObject.Object.__init__(self)

        self.service_name = None
        self.service_ident = None

        self.ip_info = ip_info
        self.port = port
        self.auth_port = auth_port

        self.untrusted_remote_machines = {}
        self.remote_machines = {}
        self.remote_registrar = None

        self.server_thread_keepalive = threading.Event()

        self.netmon = networkmonitor.get_network_monitor()

        self.server = None
        self.browser4 = None
        self.browser6 = None
        self.zeroconf = None
        self.info = None
        self.browser_mutex = threading.Lock()

        self.display_name = GLib.get_real_name()
        self.start()

    def start_zeroconf(self):
        logging.info("Using zeroconf version %s %s" % (zeroconf.__version__, "(bundled)" if config.bundle_zeroconf else ""))

        ip_addresses = []
        if self.ip_info.ip4_address is not None:
            ip_addresses.append(self.ip_info.ip4_address)
        if self.ip_info.ip6_address is not None:
            ip_addresses.append(self.ip_info.ip6_address)
        self.zeroconf = Zeroconf(interfaces=ip_addresses)

        self.service_ident = prefs.get_connect_id()
        self.service_name = "%s.%s" % (self.service_ident, SERVICE_TYPE)

        # If this process is killed (either kill or network issue), the service
        # never gets unregistered, which will prevent remotes from seeing us
        # when we come back.  Our first service info is to get us back on
        # momentarily, and the unregister properly, so remotes get notified.
        # Then we'll do it again without the flush property for the real
        # connection.

        init_info = ServiceInfo(SERVICE_TYPE,
                                self.service_name,
                                port=self.port,
                                addresses=self.ip_info.as_binary_list(),
                                properties={ 'hostname': util.get_hostname(),
                                             'type': 'flush' })

        self.zeroconf.register_service(init_info)
        time.sleep(3)
        self.zeroconf.unregister_service(init_info)
        time.sleep(3)

        self.info = ServiceInfo(SERVICE_TYPE,
                                self.service_name,
                                port=self.port,
                                addresses=self.ip_info.as_binary_list(),
                                properties={ 'hostname': util.get_hostname(),
                                             'api-version': config.RPC_API_VERSION,
                                             'auth-port': str(prefs.get_auth_port()),
                                             'type': 'real' })

        self.zeroconf.register_service(self.info)
        # ServiceBrowser can only do one IP version per instance
        if self.ip_info.ip4_address is not None:
            self.browser4 = ServiceBrowser(self.zeroconf, SERVICE_TYPE, self, addr=self.ip_info.ip4_address)
        if self.ip_info.ip6_address is not None:
            self.browser6 = ServiceBrowser(self.zeroconf, SERVICE_TYPE, self, addr=self.ip_info.ip6_address)

        return False

    # Will be mandatory eventually, this will have to be here even if we don't care about it.
    def update_service(self, zeroconf, _type, name):
        pass

    # Zeroconf worker thread
    def remove_service(self, zeroconf, _type, name):
        if name == self.service_name:
            return

        ident = name.partition(".%s" % SERVICE_TYPE)[0]

        try:
            remote = self.remote_machines[ident]
        except KeyError:
            logging.debug(">>> Discovery: unknown service ident (%s) reported as gone by zc." % ident)
            return

        logging.debug(">>> Discovery: service %s (%s:%d) has disappeared."
                          % (remote.display_hostname, remote.ip_info, remote.port))

        remote.has_zc_presence = False

    # Zeroconf worker thread
    def add_service(self, zeroconf, _type, name):
        with self.browser_mutex:
            info = zeroconf.get_service_info(_type, name)

            if info:
                ident = name.partition(".%s" % SERVICE_TYPE)[0]

                try:
                    remote_hostname = info.properties[b"hostname"].decode()
                except KeyError:
                    logging.critical(">>> Discovery: no hostname in service info properties.  Is this an old version?")
                    return

                remote_ip_info = util.RemoteInterfaceInfo(info.addresses_by_version(IPVersion.All))

                if remote_ip_info == self.ip_info:
                    return

                try:
                    # Check if this is a flush registration to reset the remote server's presence.
                    if info.properties[b"type"].decode() == "flush":
                        logging.debug(">>> Discovery: received flush service info (ignoring): %s (%s:%d)"
                                        % (remote_hostname, remote_ip_info, info.port))
                        return
                except KeyError:
                    logging.warning("No type in service info properties, assuming this is a real connect attempt")

                if ident == self.service_ident:
                    return

                try:
                    api_version = info.properties[b"api-version"].decode()
                    auth_port = int(info.properties[b"auth-port"].decode())
                except KeyError:
                    logging.debug(">>> Discovery: registration API v1 is not supported anymore, ignoring:  %s (%s)" % (remote_hostname, remote_ip_info))
                    return

                # FIXME: I'm not sure why we still get discovered by other networks in some cases -
                # The Zeroconf object has a specific ip it is set to, what more do I need to do?
                if not self.netmon.same_subnet(remote_ip_info):
                    logging.debug(">>> Discovery: service is not on this subnet, ignoring: %s (%s)" % (remote_hostname, remote_ip_info))
                    return

                cert_result = util.CertProcessingResult.FAILURE
                newly_discovered = False
                try:
                    machine = self.remote_machines[ident]
                    # Known remote machine
                    machine.has_zc_presence = True
                    logging.info(">>> Discovery: existing remote: %s (%s:%d)"
                                    % (machine.display_hostname, remote_ip_info, info.port))

                    # If the remote truly is the same one (our service info just dropped out
                    # momentarily), this will end up just retrieving the current cert again.
                    # If this was a real disconnect we didn't notice, we'll have the new cert
                    # which we'll need when our supposedly existing connection tries to continue
                    # pinging. It will fail out and restart the connection loop, and will need
                    # this updated one.

                    # This blocks the zeroconf thread.
                    if not machine.status in (RemoteStatus.INIT_CONNECTING, RemoteStatus.AWAITING_DUPLEX):
                        now = time.time()
                        if now - machine.last_register > 15: # wait at least 15 seconds after initial discovery
                            cert_result = self.remote_registrar.register(ident, remote_hostname, remote_ip_info, info.port, auth_port, api_version)
                            if cert_result == util.CertProcessingResult.FAILURE or self.server_thread_keepalive.is_set():
                                logging.warning("Register failed, or the server was shutting down during registration, ignoring remote %s (%s:%d) auth port: %d"
                                                % (remote_hostname, remote_ip_info, info.port, auth_port))
                                return

                            if machine.status == RemoteStatus.ONLINE:
                                logging.debug(">>> Discovery: rejoining existing connect with %s (%s:%d)"
                                            % (machine.display_hostname, remote_ip_info, info.port))
                                return

                            # Update our connect info if it changed.
                            machine.hostname = remote_hostname
                            machine.ip_info = remote_ip_info
                            machine.port = info.port
                            machine.api_version = api_version
                except KeyError:
                    # New remote machine
                    newly_discovered = True
                    display_hostname = self.ensure_unique_hostname(remote_hostname)

                    logging.info(">>> Discovery: new remote: %s (%s:%d)"
                                    % (display_hostname, remote_ip_info, info.port))

                    machine = remote.RemoteMachine(ident,
                                                remote_hostname,
                                                display_hostname,
                                                remote_ip_info,
                                                info.port,
                                                self.service_ident,
                                                api_version)
                    machine.last_register = time.time()
                    # This blocks the zeroconf thread. Registration will timeout
                    cert_result = self.remote_registrar.register(ident, remote_hostname, remote_ip_info, info.port, auth_port, api_version)
                    if cert_result == util.CertProcessingResult.FAILURE or self.server_thread_keepalive.is_set():
                        logging.debug("Register failed, or the server was shutting down during registration, ignoring remote %s (%s:%d) auth port: %d"
                                        % (remote_hostname, remote_ip_info, info.port, auth_port))
                        return

                    self.remote_machines[ident] = machine
                    machine.connect("ops-changed", self.remote_ops_changed)
                    machine.connect("remote-status-changed", self.remote_status_changed)
                    self.idle_emit("remote-machine-added", machine)

                machine.has_zc_presence = True

                if cert_result in (util.CertProcessingResult.CERT_INSERTED, util.CertProcessingResult.CERT_UPDATED) or \
                        (cert_result == util.CertProcessingResult.CERT_UP_TO_DATE and (newly_discovered or machine.status == RemoteStatus.OFFLINE)):
                    machine.shutdown() # This does nothing if run more than once.  It's here to make sure
                                    # the previous start thread is complete before starting a new one.
                                    # This is needed in the corner case where the remote has gone offline,
                                    # and returns before our Ping loop times out and closes the thread
                                    # itself.

                    machine.start_remote_thread()

    @misc._async
    def register_with_host(self, host:str):

        try:
            if not host.startswith("warpinator://"):
                host = "warpinator://%s" % host
            url = urllib.parse.urlparse(host)
            ipaddress.ip_address(url.hostname) # validate IPv4/IPv6 address
        except ValueError as e:
            logging.info("User tried to connect to invalid address %s" % host)
            self.idle_emit("manual-connect-result", True, False, "Invalid address")
            return

        host = url.netloc
        logging.info("Registering with " + host)
        with grpc.insecure_channel(host) as channel:
            future = grpc.channel_ready_future(channel)        
            try:
                future.result(timeout=5)
                stub = warp_pb2_grpc.WarpRegistrationStub(channel)
                reg = stub.RegisterService(warp_pb2.ServiceRegistration(service_id=self.service_ident,
                                            ip=self.ip_info.ip4_address, port=self.port,
                                            hostname=util.get_hostname(), api_version=int(config.RPC_API_VERSION),
                                            auth_port=self.auth_port, ipv6=self.ip_info.ip6_address),
                                            timeout=5)
                self.handle_manual_service_registration(reg, True)
            except Exception as e:
                future.cancel()
                logging.critical("Could not register with %s, err %s" % (host, e))
                self.idle_emit("manual-connect-result", True, False, "Could not connect to remote")

    def handle_manual_service_registration(self, reg, initiated_here=False):
        ip4_addr = None
        ip6_addr = None
        try:
            ip4_addr = ipaddress.ip_address(reg.ip)
        except ValueError:
            pass
        try:
            ip6_addr = ipaddress.ip_address(reg.ipv6)
        except ValueError:
            pass
        if reg.service_id in self.remote_machines.keys():
            # Machine already known -> update
            machine = self.remote_machines[reg.service_id]
            if machine.status == RemoteStatus.ONLINE:
                logging.debug("Host %s:%d was already connected" % (machine.ip_info, reg.auth_port))
                self.idle_emit("manual-connect-result", initiated_here, True, "Already connected")
                return
            if self.remote_registrar.register(machine.ident, machine.hostname, machine.ip_info, machine.port, reg.auth_port, machine.api_version) == util.CertProcessingResult.FAILURE or self.server_thread_keepalive.is_set():
                logging.debug("Registration of static machine failed, ignoring remote %s (%s:%d) auth %d" % (reg.hostname, machine.ip_info, reg.port, reg.auth_port))
                self.idle_emit("manual-connect-result", initiated_here, False, "Authentication failed")
                return
            machine.hostname = reg.hostname
            if isinstance(ip4_addr, ipaddress.IPv4Address):
                machine.ip_info.ip4_address = str(ip4_addr)
            if isinstance(ip6_addr, ipaddress.IPv6Address):
                machine.ip_info.ip6_address = str(ip6_addr)
            machine.port = reg.port
            machine.api_version = str(reg.api_version)

            machine.shutdown()
            machine.start_remote_thread()
        else: # New machine
            logging.debug("Adding new static machine (manual connection)")
            display_hostname = self.ensure_unique_hostname(reg.hostname)
            ip_info = util.RemoteInterfaceInfo([])
            if isinstance(ip4_addr, ipaddress.IPv4Address):
                ip_info.ip4_address = str(ip4_addr)
            if isinstance(ip6_addr, ipaddress.IPv6Address):
                ip_info.ip6_address = str(ip6_addr)
            machine = remote.RemoteMachine(reg.service_id, reg.hostname, display_hostname, ip_info, reg.port, self.service_ident, str(reg.api_version))
            if self.remote_registrar.register(machine.ident, machine.hostname, machine.ip_info, machine.port, reg.auth_port, machine.api_version) == util.CertProcessingResult.FAILURE or self.server_thread_keepalive.is_set():
                logging.debug("Registration of static machine failed, ignoring remote %s (%s:%d) auth %d"
                                    % (machine.hostname, machine.ip_info.ip4_address, machine.port, reg.auth_port))
                self.idle_emit("manual-connect-result", initiated_here, False, "Authentication failed")
                return
            self.remote_machines[machine.ident] = machine
            machine.connect("ops-changed", self.remote_ops_changed)
            machine.connect("remote-status-changed", self.remote_status_changed)
            self.idle_emit("remote-machine-added", machine)
            machine.start_remote_thread()
        self.idle_emit("manual-connect-result", initiated_here, True, "Connected")

    def ensure_unique_hostname(self, hostname):
        display_hostname = hostname
        i = 1
        while True:
            found = False

            for key in self.remote_machines.keys():
                remote_machine = self.remote_machines[key]

                if remote_machine.display_hostname == display_hostname:
                    display_hostname = "%s[%d]" % (hostname, i)
                    found = True
                    break

            i += 1
            if not found:
                break

        return display_hostname

    def run(self):
        logging.info("Using grpc version %s %s" % (grpc.__version__, "(bundled)" if config.bundle_grpc else ""))
        logging.info("Using protobuf version %s %s" % (protobuf.__version__, "(bundled)" if config.bundle_grpc else ""))
        logging.debug("Server: starting server on %s (%s)" % (self.ip_info, self.ip_info.iface))
        logging.info("Using api version %s" % config.RPC_API_VERSION)
        logging.info("Our uuid: %s" % prefs.get_connect_id())


        self.remote_registrar = remote_registration.Registrar(self.ip_info, self.port, self.auth_port)
        self.remote_registrar.reg_server_v2.service_registration_handler = self.handle_manual_service_registration
        util.initialize_rpc_threadpool()

        options=(
            ('grpc.keepalive_time_ms', 10 * 1000),
            ('grpc.keepalive_timeout_ms', 5 * 1000),
            ('grpc.keepalive_permit_without_calls', True),
            ('grpc.http2.max_pings_without_data', 0),
            ('grpc.http2.min_time_between_pings_ms', 10 * 1000),
            ('grpc.http2.min_ping_interval_without_data_ms',  5 * 1000)
        )

        self.server = grpc.server(futures.ThreadPoolExecutor(max_workers=prefs.get_server_pool_max_threads()),
                                  options=options,
                                  interceptors=[interceptors.ChunkCompressor()])
        warp_pb2_grpc.add_WarpServicer_to_server(self, self.server)

        pair = auth.get_singleton().get_server_creds()
        server_credentials = grpc.ssl_server_credentials((pair,))

        if self.ip_info.ip4_address:
            self.server.add_secure_port('%s:%d' % (self.ip_info.ip4_address, self.port),
                                        server_credentials)
        if self.ip_info.ip6_address:
            self.server.add_secure_port('[%s]:%d' % (self.ip_info.ip6_address, self.port),
                                        server_credentials)
        self.server.start()

        self.server_thread_keepalive.clear()

        try:
            self.start_zeroconf()
        except Exception as e:
            logging.critical("Zeroconf failed to start, server will terminate: %s" % e)
            self.server_thread_keepalive.set()

        self.idle_emit("server-started")

        logging.info("Server: ACTIVE")

        # **** RUNNING ****
        while not self.server_thread_keepalive.is_set():
            self.server_thread_keepalive.wait(10)
        # **** STOPPING ****

        self.remote_registrar.shutdown_registration_servers()
        self.remote_registrar = None

        logging.debug("Server: stopping discovery and advertisement")

        # If the network is down, this will probably print an exception - it's ok,
        # zeroconf catches it.
        try:
            self.zeroconf.close()
        except:
            logging.critical("Can't close Zeroconf - maybe it failed to start")
            pass

        remote_machines = list(self.remote_machines.values())
        for remote in remote_machines:
            self.idle_emit("remote-machine-removed", remote)
            logging.debug("Server: Closing connection to remote machine %s (%s:%d)"
                              % (remote.display_hostname, remote.ip_info.ip4_address, remote.port))

            remote.shutdown()

        remote_machines = None

        logging.debug("Server: terminating server")
        self.server.stop(grace=2).wait()

        self.idle_emit("shutdown-complete")
        self.server = None

        util.global_rpc_threadpool.shutdown(wait=True)
        logging.debug("Server: server stopped")

    def shutdown(self):
        self.server_thread_keepalive.set()

    def remote_status_changed(self, remote):
        if remote.status == RemoteStatus.OFFLINE:
            self.emit("remote-machine-removed", remote)

    def add_receive_op_to_remote_machine(self, op):
        self.remote_machines[op.sender].add_op(op)

    @misc._idle
    def remote_ops_changed(self, remote_machine):
        self.emit("remote-machine-ops-changed", remote_machine.ident)

    def list_remote_machines(self):
        return self.remote_machines.values()

    def get_active_op_count(self, incoming_only=False):
        count = 0

        for machine in self.remote_machines.values():
            if machine.status != RemoteStatus.ONLINE:
                continue
            for op in machine.transfer_ops:
                if incoming_only and not isinstance(op, ReceiveOp):
                    continue
                if op.status == OpStatus.TRANSFERRING:
                    count += 1

        return count

    def cancel_all_ops(self):
        for machine in self.remote_machines.values():
            if machine.status != RemoteStatus.ONLINE:
                continue
            for op in machine.transfer_ops:
                if op.status == OpStatus.TRANSFERRING:
                    op.stop_transfer()

    @misc._idle
    def idle_emit(self, signal, *callback_data):
        self.emit(signal, *callback_data)

    def Ping(self, request, context):
        logging.debug("Server Ping: from %s" % request.readable_name)

        try:
            remote = self.remote_machines[request.id]
        except KeyError as e:
            logging.debug("Server Ping: ping is from unknown remote (or not fully online yet)")

        return void

    def WaitingForDuplex(self, request, context):
        logging.debug("Server RPC: WaitingForDuplex from '%s' (api v2)" % request.readable_name)

        max_tries = 20
        i = 0

        # try for ~5 seconds (the caller aborts at 4)
        while i < max_tries:
            response = False

            try:
                remote = self.remote_machines[request.id]
                response = (remote.status in (RemoteStatus.AWAITING_DUPLEX, RemoteStatus.ONLINE))
            except KeyError:
                pass

            if response:
                break
            else:
                i += 1
                if i == max_tries:
                    context.abort(code=grpc.StatusCode.DEADLINE_EXCEEDED,
                                  details='Server timed out while waiting for his corresponding remote to connect back to you.')
                    return
                time.sleep(.25)

        return warp_pb2.HaveDuplex(response=response)

    def GetRemoteMachineInfo(self, request, context):
        logging.debug("Server RPC: GetRemoteMachineInfo from '%s'" % request.readable_name)

        return warp_pb2.RemoteMachineInfo(display_name=GLib.get_real_name(),
                                          user_name=GLib.get_user_name(),
                                          feature_flags=SERVER_FEATURES)

    def GetRemoteMachineAvatar(self, request, context):
        logging.debug("Server RPC: GetRemoteMachineAvatar from '%s'" % request.readable_name)

        path = os.path.join(GLib.get_home_dir(), ".face")
        if os.path.exists(path):
            return transfers.load_file_in_chunks(path)
        else:
            context.abort(code=grpc.StatusCode.NOT_FOUND, details='.face file not found!')

    def ProcessTransferOpRequest(self, request, context):
        logging.debug("Server RPC: ProcessTransferOpRequest from '%s'" % request.info.readable_name)

        try:
            remote_machine = self.remote_machines[request.info.ident]
        except KeyError as e:
            logging.warning("Received transfer op request for unknown remote: %s" % e)
            return

        for existing_op in remote_machine.transfer_ops:
            if existing_op.start_time == request.info.timestamp:
                # Compression could have changed for a restart, as it's not tied to the op.
                try:
                    existing_op.use_compression = request.info.use_compression
                except AttributeError:
                    existing_op.use_compression = False
                existing_op.set_status(OpStatus.WAITING_PERMISSION)
                self.add_receive_op_to_remote_machine(existing_op)
                return void

        op = ReceiveOp(request.info.ident)

        op.start_time = request.info.timestamp

        op.sender_name = request.sender_name
        op.receiver = request.receiver
        op.receiver_name = request.receiver_name
        op.status = OpStatus.WAITING_PERMISSION
        op.total_size = request.size
        op.total_count = op.remaining_count = request.count
        op.mime_if_single = request.mime_if_single
        op.name_if_single = request.name_if_single
        op.top_dir_basenames = request.top_dir_basenames

        # If request.info (grpc_pb2.OpInfo) doesn't have a use_compression field,
        # If doesn't support compression (older version of warp).
        try:
            op.use_compression = request.info.use_compression
        except AttributeError:
            op.use_compression = False

        op.connect("initial-setup-complete", self.add_receive_op_to_remote_machine)
        op.prepare_receive_info()

        return void

    def CancelTransferOpRequest(self, request, context):### good
        logging.debug("Server RPC: CancelTransferOpRequest from '%s'" % request.readable_name)

        try:
            op = self.remote_machines[request.ident].lookup_op(request.timestamp)
        except KeyError as e:
            logging.warning("Received cancel transfer op request for unknown op: %s" % e)
            return

        # If we receive this call, this means the op was cancelled remotely.  So,
        # our op with TO_REMOTE_MACHINE (we initiated it) was cancelled by the recipient.
        if op.direction == TransferDirection.TO_REMOTE_MACHINE:
            op.set_status(OpStatus.CANCELLED_PERMISSION_BY_RECEIVER)
        else:
            op.set_status(OpStatus.CANCELLED_PERMISSION_BY_SENDER)

        return void

    # receiver server responders
    def StartTransfer(self, request, context):
        logging.debug("Server RPC: StartTransfer from '%s'" % request.readable_name)

        start_time = GLib.get_monotonic_time()

        try:
            remote = self.remote_machines[request.ident]
        except KeyError as e:
            logging.warning("Server: start transfer is from unknown remote: %s" % e)
            return

        try:
            op = self.remote_machines[request.ident].lookup_op(request.timestamp)
        except KeyError as e:
            logging.warning("Server: start transfer for unknowns op: %s" % e)
            return

        cancellable = threading.Event()
        op.file_send_cancellable = cancellable

        op.set_status(OpStatus.TRANSFERRING)

        op.progress_tracker = transfers.OpProgressTracker(op)
        op.current_progress_report = None
        sender = transfers.FileSender(op, request.timestamp, cancellable)

        def transfer_done():
            if sender.error is not None:
                op.set_error(sender.error)
                op.set_status(OpStatus.FAILED_UNRECOVERABLE)
            elif op.file_send_cancellable.is_set():
                logging.debug("Server: file send cancelled")
            else:
                logging.debug("Server: transfer of %s files (%s) finished in %s" % \
                    (op.total_count, GLib.format_size(op.total_size),\
                     util.precise_format_time_span(GLib.get_monotonic_time() - start_time)))

        context.add_callback(transfer_done)
        return sender.read_chunks()

    def StopTransfer(self, request, context):
        logging.debug("Server RPC: StopTransfer from '%s'" % request.info.readable_name)

        try:
            op = self.remote_machines[request.info.ident].lookup_op(request.info.timestamp)
        except KeyError as e:
            logging.warning("Server: stop transfer was for unknown op: %s" % e)
            return

        # If we receive this call, this means the op was stopped remotely.  So,
        # our op with TO_REMOTE_MACHINE (we initiated it) was cancelled by the recipient.

        if request.error:
            op.error_msg = _("An error occurred on the remote machine")

        if op.direction == TransferDirection.TO_REMOTE_MACHINE:
            if op.file_send_cancellable is not None:
                op.file_send_cancellable.set()
            logging.debug("Server: sender received stop transfer by receiver: %s" % op.error_msg)
            if op.error_msg == "":
                op.set_status(OpStatus.STOPPED_BY_RECEIVER)
            else:
                op.set_status(OpStatus.FAILED)
        else:
            try:
                op.file_iterator.cancel()
            except AttributeError:
                # we may not have this yet if the transfer fails upon the initial response
                # (meaning we haven't returned the generator)
                pass
            logging.debug("Server: receiver received stop transfer by sender: %s" % op.error_msg)
            if op.error_msg == "":
                op.set_status(OpStatus.STOPPED_BY_SENDER)
            else:
                op.set_status(OpStatus.FAILED)

        return void

    def SendTextMessage(self, request, context):
        logging.debug("Server RPC: SendTextMessage from '%s'" % request.ident)
        try:
            remote_machine:remote.RemoteMachine = self.remote_machines[request.ident]
        except KeyError as e:
            logging.warning("Received text message from unknown remote: %s" % e)
            return
        
        op = TextMessageOp(TransferDirection.FROM_REMOTE_MACHINE, request.ident)
        op.sender_name = remote_machine.display_name
        op.message = request.message
        op.status = OpStatus.FINISHED
        remote_machine.add_op(op)
        op.send_notification()

        return void