Substitute for forking in windows

Question

I've been following Beej Networking guide and in the server section there is portion of code where it has called a function fork().

if (!fork()) { // this is the child process
            close(sockfd); // child doesn't need the listener
            if (send(new_fd, "Hello, world!", 13, 0) == -1)
                perror("send");
            close(new_fd);
            exit(0);

I'm on a windows machine and cant get that part working. What can I do to solve this?. My code is as follows.

/* Server */
#define _WIN32_WINNT 0x501
#include <iostream>
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include  <sys/types.h>


using namespace std;

const int winsockVersion = 2;
#define BACKLOG 10
#define PORT "3000"


int main(void){

    WSADATA wsadata;
    if (WSAStartup(MAKEWORD(winsockVersion,0),&wsadata) == 0){
        cout<<"-WSAStartup initialized..." << endl;

        int status;
        int sockfd, new_fd;
        const char yes = '1';
        struct addrinfo hints, *res,*loop_find;
        struct sockaddr_storage their_addr;
        socklen_t addr_size;



        memset(&hints,0,sizeof hints);
        hints.ai_family = AF_INET;
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_flags = AI_PASSIVE;

        if ( (status = getaddrinfo(NULL,PORT,&hints,&res)) == 0 ){
            cout<<"-Call to get addrinfo successful!." << endl;
        }

        for (loop_find = res; loop_find!=NULL; loop_find = loop_find->ai_next){
            if ( (sockfd = socket(loop_find->ai_family,loop_find->ai_socktype,loop_find->ai_protocol) ) == -1 ){
                cout<<"-Could not create socket." << endl;
                continue;
            }else{
                cout<<"-Socket Created." << endl;
            }

            //clearing in use ports.
            if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) {
                cout<<"-Couldnt clear blocked port." << endl;
                perror("setsockopt");
                exit(1);
            }

            if( bind(sockfd,loop_find->ai_addr,loop_find->ai_addrlen) == -1 ){
                closesocket(sockfd);
                perror("server: bind");
                continue;
            }

            break;
        }

        if (listen(sockfd,BACKLOG) != -1){
            cout<<"-Listening for incoming connections.";
        }

        //accept loop.
        while(true){

            socklen_t addr_size = sizeof their_addr;
            new_fd = accept(sockfd,(sockaddr*)&their_addr,&addr_size);

            if ( new_fd == -1 ){
                perror("accept");
                continue;
            }

            struct sockaddr new_addr;
            int len = sizeof new_addr;
            getpeername(new_fd,&new_addr,&len);
            cout<<"-Connected to " << new_addr.sa_data << endl;

            if(!fork()){ //this is a child process
                closesocket(sockfd);
                if (send(new_fd,"hello world!!",13,0) == -1){
                    perror("send");
                    closesocket(new_fd);
                    exit(0);
                }
            }
            closesocket(new_fd);

        }
    }


    //clear stuff
    if( WSACleanup() != 0){
        cout<<"-WSACleanup unsuccessful" << endl;
    }else{
        cout<<"-WSACleanup successful" << endl;
    }


    return 0;

}

Answer 1

fork does not exist on Windows. You have to use a Window specific API called CreateProcess.

Contrary to fork, CreateProcess needs the path to the EXE. You can retrieve the path of the current EXE by calling GetModuleFileName with a NULL parameter.

Answer 2

fork() obviously doesn't exist on Windows. Instead you'll need to create a new thread, or a whole new process.

Answer 3

Contrary to both existing answers (from OJ and Vincent Robert) fork() does exist on high-end versions of Windows. It's part of Subsystem for UNIX-based Applications (SUA) earlier called Microsoft Windows Services for UNIX (SFU), earlier called Interix.

Citing http://en.wikipedia.org/wiki/Interix, SUA is available on

• Windows Server 2003 R2 (all editions) - version 5.2
• Windows Vista (Ultimate and Enterprise editions) - version 6.0
• Windows Server 2008 (all editions) - version 6.0
• Windows Server 2008 R2 and Microsoft Windows 7 - version 6.1

All you have to do to use fork() is to install free SUA SDK. Depending on your target system you need one of the following:

• Utilities and Software Development Kit (SDK) for Subsystem for UNIX-based Applications
• Utilities and SDK for Subsystem for UNIX-based Applications in Microsoft Windows Vista RTM/Windows Vista SP1 and Windows Server 2008 RTM
• Utilities and SDK for Subsystem for UNIX-based Applications in Microsoft Windows 7 and Windows Server 2008 R2

You can also take a look at Does Interix implement fork()?