Re: socket communication: socket doesn't connect

"Alexander Nickolov" <>
Thu, 26 Apr 2007 11:56:10 -0700
Your server is written in C++. However, what language is your
client in? Java? C#? C++/CLI?

As far as your server code goes, you didn't post where you
accept the listening socket. With blocking socket I/O you
are supposed to spawn a new thread (or process in the original
Unix model) to handle the accepted socket and call accept
again right away. This is a terrible model for a Windows socket
server as it generates a huge amount of threads. I suggest you
investigate the other available socket programming models and
pick a better one for a server. The best scaling model is using
overlapped sockets with an I/O Completion Port (IOCP). It
is also the most complex to program. As a compromise I'd sugest
you use event-based non-blocking model via WSAEventSelect
and spawn a new thread for every 63 sockets. Combined with
a bit of thread management this should do well for a medium load
server. (The 63 comes from the limit of 64 handles you can
simultaneously wait on via WatForMultipleObjects. You need
one slot for a thread termination event, thus you have 63 slots
open for socket events. Fewer if you need additional maintenance
handles to wait for on each thread, like a waitable timer for example.)

Alexander Nickolov
Microsoft MVP [VC], MCSD

"Ananya" <> wrote in message

I am trying to establish socket communication between my C++ and Java

I bring up the Java program from the C++ program with ShellExecEx.

Then I start in the Java program with:
int port = 3000;
int rev = 1;
InetAddress address = InetAddress.getLocalHost();
Client client = new Client(port, address, rev);
int[] ints = new int[1];
ints[0] = 1;
client.send_ints(ints, 1);
using my Java Client class.

Then I continue in my C++ program with:
int port = 3000;
Server* server = new Server(port);
using my C++ Server class.

It looks like the server gets constructed properly and the connectServer
method calls the connect method from WinSock.h, which I have included (and
its library WSock32.Lib is at Additional Dependences in the Input of the

Why does this connect method from WinSock.h return - 1?

Just in case, here is the constructor of my Java Client class:
public Client(int p, InetAddress address, int rev) throws IOException,
  port = p;

     sock = new Socket(address, port);
     input = new BufferedInputStream(sock.getInputStream(), BUFFSIZE);
     output = new BufferedOutputStream(sock.getOutputStream(), BUFFSIZE);
  catch (IOException e)
  catch (IllegalArgumentException ie)

  buff = new byte[BUFFSIZE];
  data = new byte[BUFFSIZE];


and the constructor of my C++ Server class:
Server::Server(int p) throw (string)
  WSAData wsaData;
  if(WSAStartup(MAKEWORD(1,1),&wsaData) != 0)
     throw string("help!");

  port = p;

  if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
     throw string("help!");

  my_addr.sin_family = AF_INET;
  my_addr.sin_port = htons(port);
  my_addr.sin_addr.s_addr = INADDR_ANY;

  if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr))
     throw string("help!");

  if (listen(sockfd, BACKLOG) == -1)
     throw string("help!");

Thanks for your time looking at this!

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