Esempio n. 1
0
    def __init__(self):
        # {{{

        Splitter_IMS.__init__(self) #???
        #sys.stdout.write(Color.yellow)
        #print("Using DBS")
        #sys.stdout.write(Color.none)

        #self.number_of_monitors = 0
        self.peer_number = 0

        # {{{ The list of peers in the team.
        # }}}
        self.peer_list = []

        # }}}

        # {{{ Destination peers of the chunk, indexed by a chunk
        # number. Used to find the peer to which a chunk has been
        # sent.
        # }}}
        self.destination_of_chunk = [('0.0.0.0',0)] * self.BUFFER_SIZE
        #for i in range(self.BUFFER_SIZE):
        #    self.destination_of_chunk.append(('0.0.0.0',0))

        self.losses = {}
        self.magic_flags = Common.DBS
        
        _p_("max_chunk_loss =", self.MAX_CHUNK_LOSS)
        _p_("mcast_addr =", self.MCAST_ADDR)
        _p_("Initialized")
Esempio n. 2
0
    def __init__(self):

        # {{{ colorama.init()

        try:
            colorama.init()
        except Exception:
            pass

        # }}}

        # {{{ Running in debug/release mode

        _print_("Running in", end=" ")
        if __debug__:
            print("debug mode")
        else:
            print("release mode")

        # }}}

        # {{{ Arguments handling

        parser = argparse.ArgumentParser(
            description="This is the splitter node of a P2PSP team.  The splitter is in charge of defining the Set or Rules (SoR) that will control the team. By default, DBS (unicast transmissions) will be used."
        )
        # parser.add_argument('--splitter_addr', help='IP address to serve (TCP) the peers. (Default = "{}")'.format(Splitter_IMS.SPLITTER_ADDR)) <- no ahora
        parser.add_argument(
            "--buffer_size", help="size of the video buffer in blocks. Default = {}.".format(Splitter_IMS.BUFFER_SIZE)
        )
        parser.add_argument(
            "--channel",
            help='Name of the channel served by the streaming source. Default = "{}".'.format(Splitter_IMS.CHANNEL),
        )
        parser.add_argument("--chunk_size", help="Chunk size in bytes. Default = {}.".format(Splitter_IMS.CHUNK_SIZE))
        parser.add_argument(
            "--header_size",
            help="Size of the header of the stream in chunks. Default = {}.".format(Splitter_IMS.HEADER_SIZE),
        )
        parser.add_argument(
            "--max_chunk_loss",
            help="Maximum number of lost chunks for an unsupportive peer. Makes sense only in unicast mode. Default = {}.".format(
                Splitter_DBS.MAX_CHUNK_LOSS
            ),
        )
        parser.add_argument(
            "--max_number_of_monitor_peers",
            help='Maxium number of monitors in the team. The first connecting peers will automatically become monitors. Default = "{}".'.format(
                Splitter_DBS.MONITOR_NUMBER
            ),
        )
        parser.add_argument(
            "--mcast_addr",
            help='IP multicast address used to serve the chunks. Makes sense only in multicast mode. Default = "{}".'.format(
                Splitter_IMS.MCAST_ADDR
            ),
        )
        parser.add_argument("--port", help='Port to serve the peers. Default = "{}".'.format(Splitter_IMS.PORT))
        parser.add_argument(
            "--source_addr",
            help='IP address or hostname of the streaming server. Default = "{}".'.format(Splitter_IMS.SOURCE_ADDR),
        )
        parser.add_argument(
            "--source_port",
            help="Port where the streaming server is listening. Default = {}.".format(Splitter_IMS.SOURCE_PORT),
        )
        parser.add_argument(
            "--IMS",
            action="store_true",
            help="Uses the IP multicast infrastructure, if available. IMS mode is incompatible with ACS, LRS, DIS and NTS modes.",
        )
        parser.add_argument("--NTS", action="store_true", help="Enables NAT traversal.")
        parser.add_argument("--ACS", action="store_true", help="Enables Adaptive Chunk-rate.")
        parser.add_argument("--LRS", action="store_true", help="Enables Lost chunk Recovery.")
        parser.add_argument("--DIS", action="store_true", help="Enables Data Integrity check.")
        parser.add_argument("--strpe", nargs="+", type=str, help="Selects STrPe model for DIS")
        parser.add_argument("--strpeds", nargs="+", type=str, help="Selects STrPe-DS model for DIS")
        parser.add_argument("--strpeds_majority_decision", help="Sets majority decision ratio for STrPe-DS model.")
        parser.add_argument("--strpe_log", help="Logging STrPe & STrPe-DS specific data to file.")
        parser.add_argument(
            "--TTL", help="Time To Live of the multicast messages. Default = {}.".format(Splitter_IMS.TTL)
        )

        try:
            argcomplete.autocomplete(parser)
        except Exception:
            pass
        args = parser.parse_args()
        # args = parser.parse_known_args()[0]

        _print_("My IP address is =", socket.gethostbyname(socket.gethostname()))

        if args.buffer_size:
            Splitter_IMS.BUFFER_SIZE = int(args.buffer_size)
        _print_("Buffer size =", Splitter_IMS.BUFFER_SIZE)

        if args.channel:
            Splitter_IMS.CHANNEL = args.channel
        _print_('Channel = "' + Splitter_IMS.CHANNEL + '"')

        if args.chunk_size:
            Splitter_IMS.CHUNK_SIZE = int(args.chunk_size)
        _print_("Chunk size =", Splitter_IMS.CHUNK_SIZE)

        if args.header_size:
            Splitter_IMS.HEADER_SIZE = int(args.header_size)
        _print_("Header size =", Splitter_IMS.HEADER_SIZE)

        if args.port:
            Splitter_IMS.PORT = int(args.port)
        _print_("Listening port =", Splitter_IMS.PORT)

        if args.source_addr:
            Splitter_IMS.SOURCE_ADDR = socket.gethostbyname(args.source_addr)
        _print_("Source address = ", Splitter_IMS.SOURCE_ADDR)

        if args.source_port:
            Splitter_IMS.SOURCE_PORT = int(args.source_port)
        _print_("Source port =", Splitter_IMS.SOURCE_PORT)

        if args.IMS:
            _print_("IP multicast (IMS) mode selected")

            if args.mcast_addr:
                Splitter_IMS.MCAST_ADDR = args.mcast_addr
            _print_("Multicast address =", Splitter_IMS.MCAST_ADDR)

            if args.TTL:
                Splitter_IMS.TTL = args.TTL
            _print_("Multicast TTL =", Splitter_IMS.TTL)

            splitter = Splitter_IMS()
            splitter.peer_list = []  # No peer_list is used in IMS.

        else:
            _print_("IP unicast mode selected")

            if args.max_chunk_loss:
                Splitter_DBS.MAX_CHUNK_LOSS = int(args.max_chunk_loss)
            _print_("Maximun chunk loss =", Splitter_DBS.MAX_CHUNK_LOSS)

            if args.max_number_of_monitor_peers:
                Splitter_DBS.MONITOR_NUMBER = int(args.max_number_of_monitor_peers)
            _print_("Maximun number of monitor peers =", Splitter_DBS.MONITOR_NUMBER)

            splitter = Splitter_DBS()

            if args.NTS:
                splitter = Splitter_NTS(splitter)
                _print_("NTS enabled")

            if args.ACS:
                splitter = Splitter_ACS(splitter)
                _print_("ACS enabled")

            if args.LRS:
                from core.splitter_lrs import Splitter_LRS

                splitter = Splitter_LRS(splitter)
                _print_("LRS enabled")

            if args.DIS:
                from splitter_strpe import StrpeSplitter
                from splitter_strpeds import StrpeDsSplitter

                _print_("DIS enabled")
                if args.strpe:
                    splitter = Splitter_strpe(splitter)
                    print("strpe mode selected")
                    for peer in args.strpe:
                        splitter.add_trusted_peer(peer)
                if args.strpeds:
                    splitter = StrpeSplitter(splitter)
                    _print_("strpeds mode selected")
                    for peer in args.strpeds:
                        splitter.add_trusted_peer(peer)
                    if args.strpeds_majority_decision:
                        _print_("strpeds_majority_decision mode selected")
                        splitter = Splitter_strpeds_majority_decision(splitter)
                        splitter.setMajorityRatio(float(args.strpeds_majority_decision))
                if args.strpe_log:
                    splitter.LOGGING = True
                    splitter.LOG_FILE = open(strpe_log, "w", 0)

            # splitter = Splitter_ACS()
        #            if (args.strpe):
        #                splitter = self.init_strpe_splitter('strpe', args.strpe, args.strpe_log)
        #            elif (args.strpeds):
        #                splitter = self.init_strpe_splitter('strpeds', args.strpeds, args.strpe_log)
        #                if args.strpeds_majority_decision:
        #                    splitter.setMajorityRatio(float(args.strpeds_majority_decision))
        #            else:
        #                splitter = Splitter_LRS()

        # }}}

        # {{{ Run!

        splitter.start()

        # {{{ Prints information until keyboard interruption

        print("         | Received  | Sent      | Number       losses/ losses")
        print("    Time | (kbps)    | (kbps)    | peers (peer) sents   threshold period kbps")
        print("---------+-----------+-----------+-----------------------------------...")

        last_sendto_counter = splitter.sendto_counter
        last_recvfrom_counter = splitter.recvfrom_counter

        while splitter.alive:
            try:
                time.sleep(1)
                chunks_sendto = splitter.sendto_counter - last_sendto_counter
                kbps_sendto = (chunks_sendto * splitter.CHUNK_SIZE * 8) / 1000
                chunks_recvfrom = splitter.recvfrom_counter - last_recvfrom_counter
                kbps_recvfrom = (chunks_recvfrom * splitter.CHUNK_SIZE * 8) / 1000
                last_sendto_counter = splitter.sendto_counter
                last_recvfrom_counter = splitter.recvfrom_counter
                sys.stdout.write(Color.none)
                _print_("|" + repr(int(kbps_recvfrom)).rjust(10) + " |" + repr(int(kbps_sendto)).rjust(10), end=" | ")
                # print('%5d' % splitter.chunk_number, end=' ')
                sys.stdout.write(Color.cyan)
                print(len(splitter.peer_list), end=" ")
                if not __debug__:
                    counter = 0
                for p in splitter.peer_list:
                    if not __debug__:
                        if counter > 10:
                            break
                        counter += 1
                    sys.stdout.write(Color.blue)
                    print(p, end=" ")
                    sys.stdout.write(Color.red)
                    print(
                        str("%3d" % splitter.losses[p]) + "/" + str("%3d" % chunks_sendto),
                        splitter.MAX_CHUNK_LOSS,
                        end=" ",
                    )
                    if splitter is Splitter_ACS:
                        try:
                            sys.stdout.write(Color.yellow)
                            print("%3d" % splitter.period[p], end=" ")
                            sys.stdout.write(Color.purple)
                            print(
                                repr(
                                    (splitter.number_of_sent_chunks_per_peer[p] * splitter.CHUNK_SIZE * 8) / 1000
                                ).rjust(10),
                                end=" ",
                            )
                            splitter.number_of_sent_chunks_per_peer[p] = 0
                        except KeyError as e:
                            print("!", e, "--")
                            print(splitter.period[p])
                            pass
                    sys.stdout.write(Color.none)
                    print("", end=" ")
                print()

            except KeyboardInterrupt:
                print("Keyboard interrupt detected ... Exiting!")

                # Say to daemon threads that the work has been finished,
                splitter.alive = False

                # Wake up the "moderate_the_team" daemon, which is
                # waiting in a recvfrom().
                if not args.IMS:
                    # splitter.say_goodbye(("127.0.0.1", splitter.PORT), splitter.team_socket)
                    splitter.team_socket.sendto(b"", ("127.0.0.1", splitter.PORT))

                # Wake up the "handle_arrivals" daemon, which is waiting
                # in an accept().
                sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                sock.connect(("127.0.0.1", splitter.PORT))
                sock.recv(struct.calcsize("4sH"))  # Multicast channel
                sock.recv(struct.calcsize("H"))  # Header size
                sock.recv(struct.calcsize("H"))  # Chunk size
                sock.recv(splitter.CHUNK_SIZE * splitter.HEADER_SIZE)  # Header
                sock.recv(struct.calcsize("H"))  # Buffer size
                sock.recv(struct.calcsize("4sH"))  # Endpoint
                sock.recv(struct.calcsize("B"))  # Magic flags
                if args.IMS:
                    number_of_peers = 0
                else:
                    number_of_peers = socket.ntohs(struct.unpack("H", sock.recv(struct.calcsize("H")))[0])
                    print("Number of peers =", number_of_peers)
                # Receive the list
                while number_of_peers > 0:
                    sock.recv(struct.calcsize("4sH"))
                    number_of_peers -= 1

                # Breaks this thread and returns to the parent process
                # (usually, the shell).
                break
Esempio n. 3
0
 def send_configuration(self, sock):
     Splitter_IMS.send_configuration(self, sock)
     self.send_the_peer_endpoint(sock)
     self.send_magic_flags(sock)
Esempio n. 4
0
    def __init__(self):

        # {{{ colorama.init()

        try:
            colorama.init()
        except Exception:
            pass

        # }}}

        # {{{ Running in debug/release mode

        _print_("Running in", end=' ')
        if __debug__:
            print("debug mode")
        else:
            print("release mode")

        # }}}

        # {{{ Arguments handling

        parser = argparse.ArgumentParser(
            description=
            'This is the splitter node of a P2PSP team.  The splitter is in charge of defining the Set or Rules (SoR) that will control the team. By default, DBS (unicast transmissions) will be used.'
        )
        #parser.add_argument('--splitter_addr', help='IP address to serve (TCP) the peers. (Default = "{}")'.format(Splitter_IMS.SPLITTER_ADDR)) <- no ahora
        parser.add_argument(
            '--buffer_size',
            help='size of the video buffer in blocks. Default = {}.'.format(
                Splitter_IMS.BUFFER_SIZE))
        parser.add_argument(
            '--channel',
            help=
            'Name of the channel served by the streaming source. Default = "{}".'
            .format(Splitter_IMS.CHANNEL))
        parser.add_argument('--chunk_size',
                            help='Chunk size in bytes. Default = {}.'.format(
                                Splitter_IMS.CHUNK_SIZE))
        parser.add_argument(
            '--header_size',
            help='Size of the header of the stream in chunks. Default = {}.'.
            format(Splitter_IMS.HEADER_SIZE))
        parser.add_argument(
            '--max_chunk_loss',
            help=
            'Maximum number of lost chunks for an unsupportive peer. Makes sense only in unicast mode. Default = {}.'
            .format(Splitter_DBS.MAX_CHUNK_LOSS))
        parser.add_argument(
            '--max_number_of_monitor_peers',
            help=
            'Maxium number of monitors in the team. The first connecting peers will automatically become monitors. Default = "{}".'
            .format(Splitter_DBS.MONITOR_NUMBER))
        parser.add_argument(
            '--mcast_addr',
            help=
            'IP multicast address used to serve the chunks. Makes sense only in multicast mode. Default = "{}".'
            .format(Splitter_IMS.MCAST_ADDR))
        parser.add_argument(
            '--port',
            help='Port to serve the peers. Default = "{}".'.format(
                Splitter_IMS.PORT))
        parser.add_argument(
            '--source_addr',
            help=
            'IP address or hostname of the streaming server. Default = "{}".'.
            format(Splitter_IMS.SOURCE_ADDR))
        parser.add_argument(
            '--source_port',
            help='Port where the streaming server is listening. Default = {}.'.
            format(Splitter_IMS.SOURCE_PORT))
        parser.add_argument(
            "--IMS",
            action="store_true",
            help=
            "Uses the IP multicast infrastructure, if available. IMS mode is incompatible with ACS, LRS, DIS and NTS modes."
        )
        parser.add_argument("--NTS",
                            action="store_true",
                            help="Enables NAT traversal.")
        parser.add_argument("--ACS",
                            action="store_true",
                            help="Enables Adaptive Chunk-rate.")
        parser.add_argument("--LRS",
                            action="store_true",
                            help="Enables Lost chunk Recovery.")
        parser.add_argument("--DIS",
                            action="store_true",
                            help="Enables Data Integrity check.")
        parser.add_argument('--strpe',
                            nargs='+',
                            type=str,
                            help='Selects STrPe model for DIS')
        parser.add_argument('--strpeds',
                            nargs='+',
                            type=str,
                            help='Selects STrPe-DS model for DIS')
        parser.add_argument(
            '--strpeds_majority_decision',
            help='Sets majority decision ratio for STrPe-DS model.')
        parser.add_argument(
            '--strpe_log',
            help='Logging STrPe & STrPe-DS specific data to file.')
        parser.add_argument(
            '--TTL',
            help='Time To Live of the multicast messages. Default = {}.'.
            format(Splitter_IMS.TTL))

        try:
            argcomplete.autocomplete(parser)
        except Exception:
            pass
        args = parser.parse_args()
        #args = parser.parse_known_args()[0]

        _print_("My IP address is =",
                socket.gethostbyname(socket.gethostname()))

        if args.buffer_size:
            Splitter_IMS.BUFFER_SIZE = int(args.buffer_size)
        _print_("Buffer size =", Splitter_IMS.BUFFER_SIZE)

        if args.channel:
            Splitter_IMS.CHANNEL = args.channel
        _print_("Channel = \"" + Splitter_IMS.CHANNEL + "\"")

        if args.chunk_size:
            Splitter_IMS.CHUNK_SIZE = int(args.chunk_size)
        _print_("Chunk size =", Splitter_IMS.CHUNK_SIZE)

        if args.header_size:
            Splitter_IMS.HEADER_SIZE = int(args.header_size)
        _print_("Header size =", Splitter_IMS.HEADER_SIZE)

        if args.port:
            Splitter_IMS.PORT = int(args.port)
        _print_("Listening port =", Splitter_IMS.PORT)

        if args.source_addr:
            Splitter_IMS.SOURCE_ADDR = socket.gethostbyname(args.source_addr)
        _print_("Source address = ", Splitter_IMS.SOURCE_ADDR)

        if args.source_port:
            Splitter_IMS.SOURCE_PORT = int(args.source_port)
        _print_("Source port =", Splitter_IMS.SOURCE_PORT)

        if args.IMS:
            _print_("IP multicast (IMS) mode selected")

            if args.mcast_addr:
                Splitter_IMS.MCAST_ADDR = args.mcast_addr
            _print_("Multicast address =", Splitter_IMS.MCAST_ADDR)

            if args.TTL:
                Splitter_IMS.TTL = args.TTL
            _print_("Multicast TTL =", Splitter_IMS.TTL)

            splitter = Splitter_IMS()
            splitter.peer_list = []  # No peer_list is used in IMS.

        else:
            _print_("IP unicast mode selected")

            if args.max_chunk_loss:
                Splitter_DBS.MAX_CHUNK_LOSS = int(args.max_chunk_loss)
            _print_("Maximun chunk loss =", Splitter_DBS.MAX_CHUNK_LOSS)

            if args.max_number_of_monitor_peers:
                Splitter_DBS.MONITOR_NUMBER = int(
                    args.max_number_of_monitor_peers)
            _print_("Maximun number of monitor peers =",
                    Splitter_DBS.MONITOR_NUMBER)

            splitter = Splitter_DBS()

            if args.NTS:
                splitter = Splitter_NTS(splitter)
                _print_("NTS enabled")

            if args.ACS:
                splitter = Splitter_ACS(splitter)
                _print_("ACS enabled")

            if args.LRS:
                from core.splitter_lrs import Splitter_LRS
                splitter = Splitter_LRS(splitter)
                _print_("LRS enabled")

            if args.DIS:
                from splitter_strpe import StrpeSplitter
                from splitter_strpeds import StrpeDsSplitter
                _print_("DIS enabled")
                if args.strpe:
                    splitter = Splitter_strpe(splitter)
                    print("strpe mode selected")
                    for peer in args.strpe:
                        splitter.add_trusted_peer(peer)
                if args.strpeds:
                    splitter = StrpeSplitter(splitter)
                    _print_("strpeds mode selected")
                    for peer in args.strpeds:
                        splitter.add_trusted_peer(peer)
                    if args.strpeds_majority_decision:
                        _print_("strpeds_majority_decision mode selected")
                        splitter = Splitter_strpeds_majority_decision(splitter)
                        splitter.setMajorityRatio(
                            float(args.strpeds_majority_decision))
                if args.strpe_log:
                    splitter.LOGGING = True
                    splitter.LOG_FILE = open(strpe_log, 'w', 0)

            #splitter = Splitter_ACS()


#            if (args.strpe):
#                splitter = self.init_strpe_splitter('strpe', args.strpe, args.strpe_log)
#            elif (args.strpeds):
#                splitter = self.init_strpe_splitter('strpeds', args.strpeds, args.strpe_log)
#                if args.strpeds_majority_decision:
#                    splitter.setMajorityRatio(float(args.strpeds_majority_decision))
#            else:
#                splitter = Splitter_LRS()

# }}}

# {{{ Run!

        splitter.start()

        # {{{ Prints information until keyboard interruption

        print("         | Received  | Sent      | Number       losses/ losses")
        print(
            "    Time | (kbps)    | (kbps)    | peers (peer) sents   threshold period kbps"
        )
        print(
            "---------+-----------+-----------+-----------------------------------..."
        )

        last_sendto_counter = splitter.sendto_counter
        last_recvfrom_counter = splitter.recvfrom_counter

        while splitter.alive:
            try:
                time.sleep(1)
                chunks_sendto = splitter.sendto_counter - last_sendto_counter
                kbps_sendto = (chunks_sendto * splitter.CHUNK_SIZE * 8) / 1000
                chunks_recvfrom = splitter.recvfrom_counter - last_recvfrom_counter
                kbps_recvfrom = (chunks_recvfrom * splitter.CHUNK_SIZE *
                                 8) / 1000
                last_sendto_counter = splitter.sendto_counter
                last_recvfrom_counter = splitter.recvfrom_counter
                sys.stdout.write(Color.none)
                _print_("|" + repr(int(kbps_recvfrom)).rjust(10) + " |" +
                        repr(int(kbps_sendto)).rjust(10),
                        end=" | ")
                #print('%5d' % splitter.chunk_number, end=' ')
                sys.stdout.write(Color.cyan)
                print(len(splitter.peer_list), end=' ')
                if not __debug__:
                    counter = 0
                for p in splitter.peer_list:
                    if not __debug__:
                        if counter > 10:
                            break
                        counter += 1
                    sys.stdout.write(Color.blue)
                    print(p, end=' ')
                    sys.stdout.write(Color.red)
                    print(str('%3d' % splitter.losses[p]) + '/' +
                          str('%3d' % chunks_sendto),
                          splitter.MAX_CHUNK_LOSS,
                          end=' ')
                    if splitter is Splitter_ACS:
                        try:
                            sys.stdout.write(Color.yellow)
                            print('%3d' % splitter.period[p], end=' ')
                            sys.stdout.write(Color.purple)
                            print(repr(
                                (splitter.number_of_sent_chunks_per_peer[p] *
                                 splitter.CHUNK_SIZE * 8) / 1000).rjust(10),
                                  end=' ')
                            splitter.number_of_sent_chunks_per_peer[p] = 0
                        except KeyError as e:
                            print("!", e, "--")
                            print(splitter.period[p])
                            pass
                    sys.stdout.write(Color.none)
                    print('', end=' ')
                print()

            except KeyboardInterrupt:
                print('Keyboard interrupt detected ... Exiting!')

                # Say to daemon threads that the work has been finished,
                splitter.alive = False

                # Wake up the "moderate_the_team" daemon, which is
                # waiting in a recvfrom().
                if not args.IMS:
                    #splitter.say_goodbye(("127.0.0.1", splitter.PORT), splitter.team_socket)
                    splitter.team_socket.sendto(b'',
                                                ("127.0.0.1", splitter.PORT))

                # Wake up the "handle_arrivals" daemon, which is waiting
                # in an accept().
                sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                sock.connect(("127.0.0.1", splitter.PORT))
                sock.recv(struct.calcsize("4sH"))  # Multicast channel
                sock.recv(struct.calcsize("H"))  # Header size
                sock.recv(struct.calcsize("H"))  # Chunk size
                sock.recv(splitter.CHUNK_SIZE * splitter.HEADER_SIZE)  # Header
                sock.recv(struct.calcsize("H"))  # Buffer size
                sock.recv(struct.calcsize("4sH"))  # Endpoint
                sock.recv(struct.calcsize("B"))  # Magic flags
                if args.IMS:
                    number_of_peers = 0
                else:
                    number_of_peers = socket.ntohs(
                        struct.unpack("H", sock.recv(struct.calcsize("H")))[0])
                    print("Number of peers =", number_of_peers)
                # Receive the list
                while number_of_peers > 0:
                    sock.recv(struct.calcsize("4sH"))
                    number_of_peers -= 1

                # Breaks this thread and returns to the parent process
                # (usually, the shell).
                break