Connect a socket of TCP/IP on the same machine, R2009b and VC++2008 express SP1

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I tried to connect a TCP/IP socket. Before connect remote machines, I want to test the communication on the same machine.
I tested the socket program with C++ already. And It works properly.
However, when I test same routines on the C-mex file, it downs Matlab.
I wrote down the socket program as like bellows.
--- Server side ---
// Global variables for TCP/IP
int srcSocket; // this program
int dstSocket; // remote program
// sockaddr_in structure
struct sockaddr_in srcAddr;
struct sockaddr_in dstAddr;
int dstAddrSize = sizeof(dstAddr);
int status;
int numrcv;
char buffer[1024];
#define MDL_START /* Change to #undef to remove function */
#if defined(MDL_START)
static void mdlStart(SimStruct *S) {
// Initialize socket
WSAStartup(MAKEWORD(2,0), &data);
memset(&srcAddr, 0, sizeof(srcAddr));
srcAddr.sin_port = htons(PORT);
srcAddr.sin_family = AF_INET;
srcAddr.sin_addr.s_addr = htonl(INADDR_ANY); // allow any address to receive data
// open socket, stream type
srcSocket = socket(AF_INET, SOCK_STREAM, 0);
// bind sockek
bind(srcSocket, (struct sockaddr *) &srcAddr, sizeof(srcAddr));
// allow connection
listen(srcSocket, 1);
// accept connection
dstSocket = accept(srcSocket, (struct sockaddr *) &dstAddr, &dstAddrSize);
} #endif /* MDL_START */
--- Client side ---
// Global variables for TCP/IP
char destination[] = "";
int dstSocket;
struct sockaddr_in dstAddr;
char buffer[1024];
#define MDL_START /* Change to #undef to remove function */
#if defined(MDL_START)
static void mdlStart(SimStruct *S) {
WSAStartup(MAKEWORD(2,0), &data);
// Set the structure of sockaddr_in
memset( &dstAddr, 0, sizeof(dstAddr));
dstAddr.sin_port = htons(PORT);
dstAddr.sin_family = AF_INET;
dstAddr.sin_addr.s_addr = inet_addr(destination);
// Create a socket
dstSocket = socket( AF_INET, SOCK_STREAM, 0);
if( connect(dstSocket, (struct sockaddr *) &dstAddr, sizeof(dstAddr)))
// Failed to connect
connectCheck = 3;
// Success with connection
connectCheck = 8;
#endif /* MDL_START */
I put the server block and the client block on the same model file. Is it the reason of freezing Matlab? I think this is not the good way to initialize the socket between two blocks.
If someone inform me any clue, it would be great help.

Accepted Answer

Ankit Desai
Ankit Desai on 21 Jul 2011
This blog post might be helpful in trying to establish a server/client connection using TCPIP.
Remember, once you open (using fopen) the server socket, it will wait indefinitely for a connection. MATLAB will wait until an incoming connection is established.
It is therefore best to keep server and client on separate machines.
Hope this helps
  1 Comment
Sangkyun Kim
Sangkyun Kim on 22 Jul 2011
Now, I separated the server with the different process of execution file, not Matlab.
And, it works without problem. I think I need more practice with the socket programming.
Thanks for your advice.

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