客户端发送流到服务器端有几种方式，这里讨论两种：

1.客户端连接到服务器后，发送一个流，服务器接收一个流。

{*------------------------------------------------------------------------------
  客户端发送流,假定已经建立连接
------------------------------------------------------------------------------*}
procedure TClientForm.Button3Click(Sender: TObject);
var s: string; stream: TStream;
begin

try
    s := 'Hello world!';
    stream := TStringStream.Create(s);
    IdTCPClient1.OpenWriteBuffer;
    IdTCPClient1.WriteInteger(stream.Size);//注意这里：要先写入流的长度，在读取的时候如果使用 AThread.Connection.ReadStream(stream);
    IdTCPClient1.WriteStream(stream, true);
  finally
    IdTCPClient1.CloseWriteBuffer;
    stream.Free;
  end;
end;

{*------------------------------------------------------------------------------
服务器接收流
------------------------------------------------------------------------------*}
procedure TServerForm.IdTCPServer1Execute(AThread: TIdPeerThread);
var stream: Tstream;
begin

if not AThread.Terminated and AThread.Connection.Connected then
  begin
    stream := TStringStream.Create('');

AThread.Connection.ReadStream(stream);//这句相当于ReadStream(stream，-1，false)，就是根据流的前四个字节读出流长度，然后再将流读出
    stream.Position := 0;
    Memo1.Lines.LoadFromStream(stream);

end;

end;

2.客户端连接到服务器后，发送一个或多个流，当断开的时候，服务器将所有流合并在一起接收。

{*------------------------------------------------------------------------------
  客户端发送流,假定还未建立连接
------------------------------------------------------------------------------*}

procedure TClientForm.Button3Click(Sender: TObject);
var s: string; stream: TStream;
begin
  IdTCPClient1.Connect;
  try
    s := 'Hello world!';
    stream := TStringStream.Create(s);
    IdTCPClient1.OpenWriteBuffer;
    IdTCPClient1.WriteStream(stream, true);
  finally
    IdTCPClient1.CloseWriteBuffer;
    stream.Free;
    IdTCPClient1.Disconnect;
  end;
end;

{*------------------------------------------------------------------------------
服务器接收流
------------------------------------------------------------------------------*}
procedure TServerForm.IdTCPServer1Execute(AThread: TIdPeerThread);
var stream: Tstream;
begin

if not AThread.Terminated and AThread.Connection.Connected then
  begin
    stream := TStringStream.Create('');

AThread.Connection.ReadStream(stream,-1,true);//当断开连接时候接收流
    stream.Position := 0;
    Memo1.Lines.LoadFromStream(stream);

end;

end;