完成的效果图：

服务器端代码：

using System;using System.Collections.Generic;using System.Linq;using System.ServiceModel;using System.ServiceModel.Description;using System.Text;using System.Threading.Tasks;namespace SendMessageHostConsoleApplication{    [ServiceContract(SessionMode=SessionMode.Required,CallbackContract=typeof(ICallback))]    public interface IService    {        /// 
        /// 启动会话        /// 
        [OperationContract(IsOneWay=true,IsInitiating=true,IsTerminating=false)]        void Begin();        /// 
        /// 客户端调用服务器端发送消息        /// 
        ///         ///         ///         [OperationContract(IsOneWay = true)]        void SendMessage(string nick,string msg,DateTime sendTime);        /// 
        /// 终止会话        /// 
        [OperationContract(IsOneWay=true,IsInitiating=false,IsTerminating=true)]        void End();    }    public interface ICallback    {        /// 
        /// 服务器端调用客户端发送消息        /// 
        ///         ///         ///         [OperationContract(IsOneWay=true)]        void SendToClients(string nick,string msg,DateTime sendTime);    }    [ServiceBehavior(IncludeExceptionDetailInFaults=true,InstanceContextMode=InstanceContextMode.PerSession)]    public class MyService : IService    {        public static Dictionary
     
       ClientCallBacks = new Dictionary
      
       ();        public void Begin()        {            string sessionId = OperationContext.Current.SessionId;            ICallback cb = OperationContext.Current.GetCallbackChannel
       
        ();            MyService.ClientCallBacks[sessionId] = cb;        }        public void SendMessage(string nick, string msg, DateTime sendTime)        {            foreach (ICallback  c in MyService.ClientCallBacks.Values)            {                if (c != null)                {                    c.SendToClients(nick, msg, sendTime);                }            }        }        public void End()        {            string sessionId = OperationContext.Current.SessionId;            if (MyService.ClientCallBacks.ContainsKey(sessionId))            {                MyService.ClientCallBacks.Remove(sessionId);            }        }    }    public class Program    {        public static void Main(string[] args)        {            using (ServiceHost host = new ServiceHost(typeof(MyService)))            {                NetTcpBinding bingding = new NetTcpBinding();                bingding.Security.Mode = SecurityMode.None;//不需要安全模式                host.AddServiceEndpoint(typeof(IService), bingding, "net.tcp://127.0.0.1:8868/channel");                ServiceMetadataBehavior behavior = new ServiceMetadataBehavior();                behavior.HttpGetEnabled = true;                behavior.HttpGetUrl = new Uri("http://127.0.0.1:8888/WSDL"); //httpGetUrl客户端引用的地址                host.Description.Behaviors.Add(behavior);                host.Opened += delegate                {                    Console.WriteLine("服务已启动");                    Console.ReadKey();                };                host.Open();            }        }    }}
       
      
     

客户端调用代码：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.ServiceModel;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;namespace SendMessageClientWindowsFormsApplication{        public partial class Form1 : Form    {        private WS.ServiceClient client = null;        public Form1()        {            InitializeComponent();            MyCallback callback = new MyCallback();            callback.MessageReceived += callback_MessageReceived;            var instanceContext = new InstanceContext(callback);            client = new WS.ServiceClient(instanceContext);            client.Begin();            this.FormClosed += Form1_FormClosed;        }        void Form1_FormClosed(object sender, FormClosedEventArgs e)        {            client.End();        }        private void btnSend_Click(object sender, EventArgs e)        {                 client.SendMessage(this.txtNick.Text, this.txtSendMsg.Text, DateTime.Now);        }        void callback_MessageReceived(object sender, CallbackRecEventArgs e)        {            ListViewItem item = new ListViewItem();            Font font = new System.Drawing.Font(new FontFamily("宋体"), 12,FontStyle.Bold);            item.Font = font;            item.ForeColor = Color.Blue;            if (e.Nick == this.txtNick.Text)            {                item.ForeColor = Color.Green;            }            item.Text = e.Nick + "        " + e.SendTime+"\r\n";            listView1.Items.Add(item);            listView1.Items.Add(e.Message);            this.txtSendMsg.Text = "";        }    }    public class MyCallback : WS.IServiceCallback    {        public void SendToClients(string nick, string msg, DateTime sendTime)        {            if (this.MessageReceived != null)            {                CallbackRecEventArgs arg = new CallbackRecEventArgs(nick, msg, sendTime);                this.MessageReceived(this, arg);            }        }        public event EventHandler
     
       MessageReceived;    }    public class CallbackRecEventArgs : EventArgs    {        private string _Nick, _Msg;        private DateTime _time;        public CallbackRecEventArgs(string nk, string m, DateTime t)        {            _Nick = nk;            _Msg = m;            _time = t;        }        public string Nick        {            get { return _Nick; }        }        public string Message        {            get { return _Msg; }        }        public DateTime SendTime        {            get { return _time; }        }    }}