WSASend report "本地网络终止连接" when another tcpconnection buf full

[weixin_38051479]

I'm sure that boost::asio use WSASend to send message, But I don't know how asio was getting the result of send.
I wrote a tcp server by boost::asio, send many many message to clients. One of the clients paused(such as pause by debugger or recv msg is paused by scanf), others run normally.
When the client paused, the memory load of the server increased fast. A few minutes later,  serval clients was report error "本地网络终止连接"(it means local network terminated).
I don't know why those clients run successfully but a few minutes later they got error. Could you explain it?