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From: "A. Dalton" <garibaldi_cpp AT hotmail DOT com>
To: cygwin AT sources DOT redhat DOT com
Subject: AF_UNIX Socket Programming
Date: Mon, 21 Aug 2000 10:39:14 EDT
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Message-ID: <F176PGtPrPrvCWO6hm800002e1a@hotmail.com>

Greetings,

I have been able to install Cygwin (thanks to the nice little setup 
program).  Now I am trying to do some basic AF_UNIX socket programming.  I 
have copied an example from the following URL:

http://www.informatik.hu-berlin.de/~mueller/dsm/www.wrox.com/books/680/680.html

In this example, a server and a client that communicate via a socket.  
Everything compiles correctly but when I run it, nothing happens.  It 
appears that the accept() in the server fails.  Whenever I include the 
printf() for "server waiting," I see that I'm in a hard loop.  The accept() 
doesn't seem to block.  The exact same code works in Linux.  Here's the code 
I'm using:

//**********************************************************************

//
// Server.cpp
//
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdio.h>

int main()
{
    int         server_sockfd;
    int         client_sockfd;
    int         server_len;
    int         client_len;
    sockaddr_un server_address;
    sockaddr_un client_address;

    unlink("server_socket");
    server_sockfd = socket(AF_UNIX, SOCK_STREAM, 0);

    server_address.sun_family = AF_UNIX;
    strcpy(server_address.sun_path, "server_socket");
    server_len = sizeof(server_address);
    bind(server_sockfd, (sockaddr*)&server_address, server_len);

    listen(server_sockfd, 5);
    while(true)
    {
        char ch;

        // printf("server waiting\n");

        client_sockfd = accept(server_sockfd,
                        (sockaddr*)&client_address,
                        &client_len);

        read(client_sockfd, &ch, 1);
        ++ch;
        write(client_sockfd, &ch, 1);
        close(client_sockfd);
    }
}

//**********************************************************************

//
// Client.cpp
//
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdio.h>

int main()
{
    int         sockfd;
    int         len;
    sockaddr_un address;
    int         result;
    char        ch       = 'A';

    sockfd = socket(AF_UNIX, SOCK_STREAM, 0);

    address.sun_family = AF_UNIX;
    strcpy(address.sun_path, "server_socket");
    len = sizeof(address);

    result = connect(sockfd, (sockaddr*)&address, len);

    if(result == -1)
    {
        perror("oops:  client1");
        exit(1);
    }

    write(sockfd, &ch, 1);
    read(sockfd, &ch, 1);
    printf("char from server = %c\n", ch);
    close(sockfd);
    exit(0);
}

//**********************************************************************

ad24482 AT GARIBALDI ~
$ g++ -Wall -o server server.cpp

ad24482 AT GARIBALDI ~
$ g++ -Wall -o client client.cpp

ad24482 AT GARIBALDI ~
$ server&
[1] 1015

ad24482 AT GARIBALDI ~
$ client

// In theory, I should see "char from server = B" here

The server does seem to create the socket file:

ad24482 AT GARIBALDI ~
$ ls -lap server_socket
srw-r--r--   1 ad24482  unknown        15 Aug 21 10:30 server_socket=

ad24482 AT GARIBALDI ~
$ g++ --version
2.95.2

ad24482 AT GARIBALDI ~
$


If anyone has any idea what is wrong, I could really use some help.  Thanks 
in advance for your time.

Andy
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