[chrismonsanto]

Working directory can be changed on a per-thread basis on Mac with pthread_chdir_np, and on Linux you can create a thread with the clone syscall and without the CLONE_FS flag to avoid sharing working directory with the rest of the process. I don't know about Windows.

[skissane]

I think the answer on Windows is "No".

One could fork a subprocess, chdir()+socket() there, then pass the socket back to parent over another socket (opened maybe with socketpair().) Should work on any Unix-like which supports SCM_RIGHTS (which is almost everybody, apparently even obscure platforms like AIX, IBM i, z/OS). But not Windows, which doesn't (at least not yet, they may add it at some point.)

Makes one really wish there was a bindat() call:

  int bindat(int sockfd, const struct sockaddr *addr, socklen_t addrlen, int dirfd);

or maybe funixsockat:

  int funixsockat(int type, int dirfd, const char * name);

which would combine socket() and bind() in a single call

[jstarks]

In Windows we actually have a way to set the parent directory for a UDS bind or connect, via a socket ioctl. It’s not documented yet, but it’s in the header.