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Date: Mon, 7 Apr 2025 17:39:37 +0900
To: cygwin AT cygwin DOT com
Subject: Re: unix socket hang when connect
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From: Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
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On Mon,  7 Apr 2025 15:08:32 +0800
Yuyi Wang wrote:
> Below is a simple unix socket testing code. It creates a unix socket server and
> a client to connect to it immediately. It works on Linux and macOS, but hangs on
> cygwin. bind + listen work well, but seems that the connect method never returns.
> 
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <unistd.h>
> #include <sys/socket.h>
> #include <sys/un.h>
> #include <errno.h>
> 
> #define SOCKET_PATH "/tmp/example_socket"
> 
> int main() {
>     int server_fd, client_fd;
>     struct sockaddr_un server_addr;
>     socklen_t client_len;
> 
>     server_fd = socket(AF_UNIX, SOCK_STREAM, 0);
>     if (server_fd == -1) {
>         perror("server socket");
>         exit(EXIT_FAILURE);
>     }
> 
>     memset(&server_addr, 0, sizeof(server_addr));
>     server_addr.sun_family = AF_UNIX;
>     strncpy(server_addr.sun_path, SOCKET_PATH, sizeof(server_addr.sun_path) - 1);
> 
>     if (bind(server_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
>         perror("bind");
>         exit(EXIT_FAILURE);
>     }
> 
>     if (listen(server_fd, 1) == -1) {
>         perror("listen");
>         exit(EXIT_FAILURE);
>     }
> 
>     printf("Server is listening on %s\n", SOCKET_PATH);
> 
>     client_fd = socket(AF_UNIX, SOCK_STREAM, 0);
>     if (client_fd == -1) {
>         perror("client socket");
>         exit(EXIT_FAILURE);
>     }
> 
>     if (connect(client_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
>         perror("connect");
>         exit(EXIT_FAILURE);
>     }
> 
>     printf("Client connected to server\n");
> 
>     close(client_fd);
>     close(server_fd);
>     unlink(SOCKET_PATH);
> 
>     return 0;
> }

I guess connect() just is just waiting accept().

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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