SetTimeOut for Winsock2 in C

The errors on sockets seem to be globals -- some integer somewhere is popped to the most recent error code and accessed with a "getlasterror" function. (wsagetlasterror?? something like this, names escape me).

To make it not wait, you want to set the socket to "notblocking" at which point the socket will read, nothing there, pass thru ... this is not the default so you must set this socket option. (setsocketopt?) or wsasetsocketopt or something like that.

You should be able to send or recieve from the same socket. Use sendto & recievefrom functions (udp & tcp might have slightly different names).

You have to make sure all the stuff is set up properly, but I know this is doable as my sockets are all read & write. (I have some very, very simple udp code if you want me to dig it out, its ugly -- cut and pasted from some examples and poked it until it worked).

In most cases, you will be able to view the errors by examining errno, which is a global integer or in a mutithreaded environment, an implicit function call which returns the latest error code of the application.

From your original post, it sounds like you want the "read" to return even if there is nothing there. This is called a "non blocking read".

long nonblocking = TRUE;
ioctlsocket(Socket, FIONBIO, &nonblocking);

Something like that. You'll find the read call returns immediatley after making your socket non blocking with this call.

See http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/winsock/ioctlsocket_2.asp for more info.

Fixed smiles

The examples in visual studio 6.0 are in C (or nearly so, its supposedly C++).
Starting with .net microsoft hid the low level examples.

The following class was created from those C examples, which I can no longer find.
It is basically C in the class methods. I wrote it assuming threaded apps but that is not required if you use the nonblocking IO statements provided by Peter. Anyway, this might help you create the C you need, if not throw it away.

//// .h file

/*simple udp and tcp library

This is supposed to be able to perform most udp and tcp functions.
I am not sure how much of tcp works anymore; UDP is working well.

*/

#ifndef jcomm_file
#define jcomm_file

#define WIN32_LEAN_AND_MEAN

typedef int socklen_t;
#include <afxwin.h> //threads
#include <winsock.h> //this one messes up in .net, the other in 6.0 so whatever
//#include <winsock2.h> //the example included this but it causes problems!

typedef float float_data_t[1024]; //you could make this something else, a struct, etc.
const int size_of_datagram = 4096;
//I assume here that a float is 4 bytes ! seems fair as this stuff needs visual studio to compile...
//tc uses send to send from server back to client, udp uses sendto, I did not have a use for this yet.

struct jcomm_t
{
char *host;
unsigned int port;
char data[size_of_datagram];
bool udp; //udp or tcpip?

void jcomm_t::jcomm_client_init(int portnum, char * host_name, bool is_udp);
void jcomm_t::jcomm_client_send(); //example mostly (use sendto instead)

void jcomm_t::jcomm_server_init(int portnum, bool is_udp);
void jcomm_t::jcomm_server_start(); //example do not use
void jcomm_t::jcomm_cleanup(); //?? it may break all sockets not just this one

static bool jcomm_show_error(); //the help text for each code is printed
sockaddr_in server, local, from;

PHOSTENT phostent;
WSADATA WSAData;
SOCKET WinSocket,tcsocket;

unsigned int Addr;
int fromlen;
};
#endif

------ //end .h

//1-31-05 -- borrows heavily from microsoft examples --

#include "udp-tcp.h"
#include <iostream>
using namespace std;

void jcomm_t::jcomm_client_init(int portnum, char * host_name, bool is_udp)//func
{
// Notice that almost nothing in this code is specific to whether we
// are using UDP or TCP. The socket open command is the only place.
// When connect() is called on a udp socket, it does not
// actually establish the connection as a TCP socket
// would. Instead, TCP establishes the remote half of the
// ( LocalIPAddress, LocalPort, RemoteIP, RemotePort) mapping.
// This enables us to use send() and recv() on datagram sockets,
// instead of recvfrom() and sendto() -- making this a generic object
//suited for either tcp or udp transmission

port = portnum;
host = host_name;
udp = is_udp;

WSAStartup(0x202,&WSAData); //X202 is 514 decimal, it is the 'version required' of something or other.

if (isalpha(host[0])) //if its a Name or a number, we can open it either way
{
phostent = gethostbyname(host);
}
else
{
Addr = inet_addr(host);
phostent = gethostbyaddr((char *)&Addr,4,AF_INET);
}

memset(&server,0,sizeof(server));
memcpy(&(server.sin_addr),phostent ->h_addr,phostent ->h_length);
server.sin_family = phostent ->h_addrtype;
server.sin_port = htons(port);


if(udp)
WinSocket = socket(AF_INET,SOCK_DGRAM,0); // Open a socket udp style
else
{
WinSocket = socket(AF_INET,SOCK_STREAM,0); // Open a socket tcp style
}

/*
local.sin_family = AF_INET;
local.sin_addr.s_addr = INADDR_ANY; //inet_addr("204.130.141.139"); //could be set to an ip address
local.sin_port = htons(port);
cout << local.sin_port << endl;

bool val = true;
setsockopt(WinSocket,IPPROTO_IP,SO_REUSEADDR, (char *) &val, sizeof(bool));
bind(WinSocket,(sockaddr*)&local,sizeof(local) );
*/
connect(WinSocket ,(sockaddr*)&server,sizeof(server)) ;

/*
sockaddr getsa;
int namelen;
getsockname (WinSocket,&getsa, &namelen );
int x;
for(x = 0; x < namelen; x++)
printf("%x",getsa.sa_data[x]);
cout << endl;
*/
jcomm_show_error();
}

void jcomm_t::jcomm_client_send()//func
{
send(WinSocket, data, size_of_datagram ,0);
}

void jcomm_t::jcomm_server_init(int portnum, bool is_udp)//func
{
port = portnum;
udp = is_udp;

WSAStartup(0x202,&WSAData);
local.sin_family = AF_INET;
local.sin_addr.s_addr = INADDR_ANY; //could be set to an ip address
local.sin_port = htons(port);
if(udp)
WinSocket= socket(AF_INET, SOCK_DGRAM ,0); //udp
else
WinSocket= socket(AF_INET, SOCK_STREAM,0); //tcp

bind(WinSocket,(sockaddr*)&local,sizeof(local) );
// We cannot listen() on a UDP socket.

fromlen =sizeof(from);

if (!udp)
{
listen(WinSocket,100);
tcsocket = accept(WinSocket,(struct sockaddr*)&from, &fromlen);
inet_ntoa(from.sin_addr),
htons(from.sin_port) ;
/**/
}
else
tcsocket = WinSocket;
}

//the threads should be customized to handle your packets or do what you need
//they are provided as examples / templates !

UINT jcomm_tcpip_thread(LPVOID pointer)//func
{
jcomm_t * pj = (jcomm_t *) pointer;

listen(pj->WinSocket,5);
pj->fromlen =sizeof(pj->from);
pj->tcsocket = accept(pj->WinSocket,(sockaddr*)&(pj->from), &(pj->fromlen));
inet_ntoa(pj->from.sin_addr);
htons(pj->from.sin_port) ;

/*
for(;;)
{
recv(pj->tcsocket,pj->data,size_of_datagram,0 );
//process data here
}
*/
return 0;
}

UINT jcomm_udp_thread(LPVOID pointer)//func
{
jcomm_t * pj = (jcomm_t *) pointer;
for(;;)
{
recvfrom(pj->tcsocket,pj->data,size_of_datagram,0,
(sockaddr *)&(pj->from),&(pj->fromlen));
//process data here
}
return 0;
}

void jcomm_t::jcomm_server_start()//func
{
if(udp)
AfxBeginThread(jcomm_udp_thread, this, THREAD_PRIORITY_LOWEST, 0, 0, NULL);
else
AfxBeginThread(jcomm_tcpip_thread, this, THREAD_PRIORITY_LOWEST, 0, 0, NULL);
}

void jcomm_t::jcomm_cleanup()//func
{
closesocket(WinSocket);
WSACleanup();
}