C#

• building a configuration (port, transport, security) driven client/server system
  
• implementing both sync and async client APIs
  
• adding hooks (e.g. custom compression) before data is sent/received
  
• implementing logging and instrumenting traffic
  
• implementing handshaking (full-duplex) communication and transacted communication
  
• embedding the server in any type of host host (GUI app, console app, web app, Windows service)

• WCF Introduction - Part1[^] (CP) <-- recommended
  
• WCF Getting Started[^] (MSDN)

Chesnokov Yuriy wrote:

I've seen those samples with a server getting back data from a client, sending back response and closing it.

I'm intrested in a server handing many clients connected and client connected to many servers architecture.

Chesnokov Yuriy wrote:

There should be some ready described solutions to avoid common mistakes.

Bastard Programmer from Hell

class Employee 
        {
            public void Talk()
            {
                MessageBox.Show("I am an Employee.");
            }
        }

        class ContractEmployee: Employee 
        {
            public void ContractTalk()
            {
                MessageBox.Show("I am a Contract Employee.");
            }
        }

static void CreateEmployee()
        {
            Employee e = new ContractEmployee();
            e.Talk();
            e.ContractTalk();
        }

interface IEmployee
        {
            void Talk();
        }

        abstract class Employee : IEmployee
        {
            public abstract void Talk();
        }

        class PermanentEmployee:Employee
        {
            public override void Talk()
            {
                MessageBox.Show("I am a Permanent Employee.");
            }
        }

        class ContractEmployee: Employee 
        {
            public override void Talk()
            {
                MessageBox.Show("I am a Contract Employee.");
            }
        }

static void CreateEmployee()
        {
            Employee e = new ContractEmployee();
            e.Talk();
            e = new PermanentEmployee();
            e.Talk();
        }