IPv4-only Server Code
The following code is the Simples.c file, which is an IPv4-only Windows Sockets server (an IPv6-enabled version of the Simples.c file can be found in Appendix B). This code is provided for comparison purposes only — use Appendix B for an example of how to write an IPv6-enabled server.
/******************************************************************************\
* simples.c - Simple TCP/UDP server using Winsock 1.1
* This is a part of the Microsoft<entity type="reg"/> Source Code Samples.
* Copyright 1996 - 2000 Microsoft Corporation.
* All rights reserved.
* This source code is only intended as a supplement to
* Microsoft Development Tools and/or WinHelp documentation.
* See these sources for detailed information regarding the
* Microsoft samples programs.
\******************************************************************************/
#define WIN32_LEAN_AND_MEAN
#include <winsock2.h>
#include <Ws2tcpip.h>
#include <stdio.h>
#include <stdlib.h>
// Link with ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")
#define STRICMP _stricmp
#define DEFAULT_PORT 5001
#define DEFAULT_PROTO SOCK_STREAM // TCP
void Usage(char *progname) {
fprintf(stderr,"Usage\n%s -p [protocol] -e [endpoint] -i [interface]\n",
progname);
fprintf(stderr,"Where:\n\tprotocol is one of TCP or UDP\n");
fprintf(stderr,"\tendpoint is the port to listen on\n");
fprintf(stderr,"\tinterface is the ipaddr (in dotted decimal notation)");
fprintf(stderr," to bind to\n");
fprintf(stderr,"Defaults are TCP,5001 and INADDR_ANY\n");
WSACleanup();
exit(1);
}
int main(int argc, char **argv) {
char Buffer[128];
char *interface= NULL;
unsigned short port=DEFAULT_PORT;
int retval;
int fromlen;
int i;
int socket_type = DEFAULT_PROTO;
struct sockaddr_in local, from;
WSADATA wsaData;
SOCKET listen_socket, msgsock;
/* Parse arguments */
if (argc >1) {
for(i=1;i <argc;i++) {
if ( (argv[i][0] == '-') || (argv[i][0] == '/') ) {
switch(tolower(argv[i][1])) {
case 'p':
if (!STRICMP(argv[i+1], "TCP") )
socket_type = SOCK_STREAM;
else if (!STRICMP(argv[i+1], "UDP") )
socket_type = SOCK_DGRAM;
else
Usage(argv[0]);
i++;
break;
case 'i':
interface = argv[++i];
break;
case 'e':
port = (unsigned short) atoi(argv[++i]);
break;
default:
Usage(argv[0]);
break;
}
}
else
Usage(argv[0]);
}
}
if ((retval = WSAStartup(0x202,&wsaData)) != 0) {
fprintf(stderr,"WSAStartup failed with error %d\n",retval);
WSACleanup();
return -1;
}
if (port == 0){
Usage(argv[0]);
}
local.sin_family = AF_INET;
local.sin_addr.s_addr = (!interface)?INADDR_ANY:inet_addr(interface);
/*
* Port MUST be in Network Byte Order
*/
local.sin_port = htons(port);
listen_socket = socket(AF_INET, socket_type,0); // TCP socket
if (listen_socket == INVALID_SOCKET){
fprintf(stderr,"socket() failed with error %d\n",WSAGetLastError());
WSACleanup();
return -1;
}
//
// bind() associates a local address and port combination with the
// socket just created. This is most useful when the application is a
// server that has a well-known port that clients know about in advance.
//
if (bind(listen_socket,(struct sockaddr*)&local,sizeof(local) )
== SOCKET_ERROR) {
fprintf(stderr,"bind() failed with error %d\n",WSAGetLastError());
WSACleanup();
return -1;
}
//
// So far, everything we did was applicable to TCP as well as UDP.
// However, there are certain steps that do not work when the server is
// using UDP.
//
// We cannot listen() on a UDP socket.
if (socket_type != SOCK_DGRAM) {
if (listen(listen_socket,5) == SOCKET_ERROR) {
fprintf(stderr,"listen() failed with error %d\n",WSAGetLastError());
WSACleanup();
return -1;
}
}
printf("%s: 'Listening' on port %d, protocol %s\n",argv[0],port,
(socket_type == SOCK_STREAM)?"TCP":"UDP");
while(1) {
fromlen =sizeof(from);
//
// accept() doesn't make sense on UDP, since we do not listen()
//
if (socket_type != SOCK_DGRAM) {
msgsock = accept(listen_socket,(struct sockaddr*)&from, &fromlen);
if (msgsock == INVALID_SOCKET) {
fprintf(stderr,"accept() error %d\n",WSAGetLastError());
WSACleanup();
return -1;
}
printf("accepted connection from %s, port %d\n",
inet_ntoa(from.sin_addr),
htons(from.sin_port)) ;
}
else
msgsock = listen_socket;
//
// In the case of SOCK_STREAM, the server can do recv() and
// send() on the accepted socket and then close it.
// However, for SOCK_DGRAM (UDP), the server will do
// recvfrom() and sendto() in a loop.
if (socket_type != SOCK_DGRAM)
retval = recv(msgsock,Buffer,sizeof (Buffer),0 );
else {
retval = recvfrom(msgsock,Buffer,sizeof (Buffer),0,
(struct sockaddr *)&from,&fromlen);
printf("Received datagram from %s\n",inet_ntoa(from.sin_addr));
}
if (retval == SOCKET_ERROR) {
fprintf(stderr,"recv() failed: error %d\n",WSAGetLastError());
closesocket(msgsock);
continue;
}
if (retval == 0) {
printf("Client closed connection\n");
closesocket(msgsock);
continue;
}
printf("Received %d bytes, data [%s] from client\n",retval,Buffer);
printf("Echoing same data back to client\n");
if (socket_type != SOCK_DGRAM)
retval = send(msgsock,Buffer,sizeof(Buffer),0);
else
retval = sendto(msgsock,Buffer,sizeof (Buffer),0,
(struct sockaddr *)&from,fromlen);
if (retval == SOCKET_ERROR) {
fprintf(stderr,"send() failed: error %d\n",WSAGetLastError());
}
if (socket_type != SOCK_DGRAM){
printf("Terminating connection\n");
closesocket(msgsock);
}
else
printf("UDP server looping back for more requests\n");
continue;
}
}