using System;
using System.IO;
using System.ServiceModel;
using System.Text;
using System.Timers;

namespace StockLibraryStreaming
{
    [ServiceContract(SessionMode = SessionMode.Allowed)]
    public interface ServiceContract
    {
        [OperationContract]
        string GetData(int value);

        [OperationContract]
        Stream GetSteram();
    }

    [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession, ConcurrencyMode = ConcurrencyMode.Multiple)]
    public class ServiceImplementation : ServiceContract
    {
        private readonly Stream fStream;
        private readonly Timer fTimer;

        public ServiceImplementation()
        {
            var _buffer = Encoding.ASCII.GetBytes(@"Hello, World!");

            fStream = new MemoryStream();
            fStream.Write(_buffer, 0, _buffer.Length);
            fStream.Position = 0;

            fTimer = new Timer(10);
            fTimer.Elapsed += fTimer_Elapsed;
            fTimer.Start();
        }

        void fTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            var _buffer = Encoding.ASCII.GetBytes(DateTime.Now.ToString());

            fStream.Write(_buffer, 0, _buffer.Length); // <-- ошибка в этой строке
        }

        #region ServiceContract Members

        public string GetData(int value)
        {
            return value.ToString();
        }

        public Stream GetSteram()
        {
            return fStream; 
        }

        #endregion
    }
}

using System;
using System.IO;
using System.Text;
using System.Threading;
using ConsoleClient.Srv;

namespace ConsoleClient
{
    class Program
    {
        private static ServiceContractClient fProxy;
        private static Thread fThread1;
        private static Thread fThread2;

        static void Main(string[] args)
        {
            fProxy = new ServiceContractClient();

            fThread1 = new Thread(FGetInt) {IsBackground = true};
            fThread2 = new Thread(FGetString) {IsBackground = true};

            fThread1.Start(fProxy);
            fThread2.Start(fProxy);

            Console.ReadLine();
        }

        private static void FGetInt(object obj)
        {
            var _proxy = (ServiceContractClient) obj;
            var _rnd = new Random();

            while (true)
            {
                Console.WriteLine(_proxy.GetData(_rnd.Next(0, 101)));
                Thread.Sleep(1000);
            }
        }

        private static void FGetString(object obj)
        {
            var _proxy = (ServiceContractClient)obj;
            Stream _stream = _proxy.GetSteram();

            while (true)
            {
                var _buffer = new byte[50];
                int _readed = _stream.Read(_buffer, 0, _buffer.Length);

                Console.WriteLine(Encoding.ASCII.GetString(_buffer, 0, _readed));
                Thread.Sleep(1000);
            }
        }
    }
}

<configuration>
    <system.serviceModel>
        <bindings>
            <netTcpBinding>
                <binding name="NewBinding0" transferMode="Streamed" />
            </netTcpBinding>
        </bindings>
        <behaviors>
            <serviceBehaviors>
                <behavior name="NewBehavior">
                    <serviceMetadata httpGetEnabled="true" />
                </behavior>
            </serviceBehaviors>
        </behaviors>
        <services>
            <service behaviorConfiguration="NewBehavior" name="StockLibraryStreaming.ServiceImplementation">
                <clear />
                <endpoint address="" binding="netTcpBinding" bindingConfiguration="NewBinding0"
                    name="StreamTCP" contract="StockLibraryStreaming.ServiceContract"
                    listenUriMode="Explicit" />
                <endpoint address="" binding="mexHttpBinding" bindingConfiguration=""
                    name="StreamMEX" contract="IMetadataExchange" />
                <host>
                    <baseAddresses>
                        <add baseAddress="net.tcp://localhost:8888" />
                        <add baseAddress=" http://localhost:8889"  />
                    </baseAddresses>
                </host>
            </service>
        </services>
    </system.serviceModel>
</configuration>

<configuration>
    <system.serviceModel>
        <bindings>
            <netTcpBinding>
                <binding name="StreamTCP" closeTimeout="00:01:00" openTimeout="00:01:00"
                    receiveTimeout="00:10:00" sendTimeout="00:01:00" transactionFlow="false"
                    transferMode="Streamed" transactionProtocol="OleTransactions"
                    hostNameComparisonMode="StrongWildcard" listenBacklog="10"
                    maxBufferPoolSize="524288" maxBufferSize="65536" maxConnections="10"
                    maxReceivedMessageSize="65536">
                    <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
                        maxBytesPerRead="4096" maxNameTableCharCount="16384" />
                    <reliableSession ordered="true" inactivityTimeout="00:10:00"
                        enabled="false" />
                    <security mode="Transport">
                        <transport clientCredentialType="Windows" protectionLevel="EncryptAndSign" />
                        <message clientCredentialType="Windows" />
                    </security>
                </binding>
            </netTcpBinding>
        </bindings>
        <client>
            <endpoint address="net.tcp://localhost:8888/" binding="netTcpBinding"
                bindingConfiguration="StreamTCP" contract="Srv.ServiceContract"
                name="StreamTCP">
            </endpoint>
        </client>
    </system.serviceModel>
</configuration>