套接字发送客户端列表

Question

I'm not very skilled in C#, but I'm using it for an homework. I created a function to send a list of clients connected to a server to the other clients

private void SendListToClients()
    {
        Socket userSocket=null;
        string username = null;
        string role = null;
        foreach (User Users in UserList)
        {
            userSocket = Users.getSocket();
            username = Users.getUsername();
            role = Users.getRole();
            userSocket.Send(Encoding.ASCII.GetBytes("!ListStart\n"));
            for(int i=0;i<UserList.Count;i++)
            {
                User UsersControl = (User)UserList[i];
                string roleU = UsersControl.getRole();
                string usernameU = UsersControl.getUsername();

                userSocket.Send(Encoding.ASCII.GetBytes("!ClientList:"+usernameU + ":" + roleU+"\n"));       
            }

        }
    }

My problem is in the line userSocket.Send(), when I receive this at the client side I don't receive (if the user in the list are 5 for example) 5 send, but 1 send with all the 5 users. How can I solve this? Otherwise there's the possibility to send my Object (UserList) enterly over the socket?

Answer 1

From the Socket.Receive Method documentation:

If you are using a connection-oriented Socket, the Receive method will read as much data as is available, up to the size of the buffer.

Hence, even though the server sent five messages one at a time, all of them were stored in the client's input buffer and read at once.

Answer 2

What you are seeing is by design. This is how TCP works. Or as others will tell you, "TCP is a stream protocol, not a message protocol."

Short summary: Just because you "sent" N bytes, doesn't mean you will "receive" N bytes. TCP will stream the bytes independent of how the app structured its "send" calls. Your receive side code should be prepared to handle receiving byte chunks of all different sizes and not necessarily in blocks equal to your applications message size