std.posix.send: should expect ConnectionRefused

[pseudocc]

Closes: #20219

[pseudocc]

flake.nix (apply this patch on top of 0.14.1).

{
  description = "Verify a patch for Zig";

  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-25.05";

  outputs = { self, nixpkgs }: import ./nix/each-system.nix nixpkgs (
    system: pkgs: let
      inherit (pkgs) lib;
      name = "poc";
      zig = pkgs.zig.overrideAttrs {
        patches = pkgs.fetchurl {
          url = "https://github.com/ziglang/zig/pull/24365.patch";
          hash = "sha256-3ZaebBTfKeMEPr5XK+2UfMAao0zR+WuP34bINr7SsDA=";
        };
      };
    in {
      devShells.default = pkgs.mkShell {
        buildInputs = [ zig ];
      };
    }
  );
}

main.zig (copied from comment)

const std = @import("std");

pub fn main() !void {
    const socket = try std.posix.socket(std.posix.AF.INET, std.posix.SOCK.DGRAM, 0);
    const address = std.net.Address.parseIp4("0.0.0.0", 9999) catch unreachable;
    try std.posix.connect(socket, &address.any, address.getOsSockLen());

    var i: usize = 0;
    while (i < 2) : (i = i + 1) {
        _ = try std.posix.send(socket, "hello", 0);
        std.time.sleep(10 * std.time.ns_per_ms);
    }
    std.debug.print("ok?\n", .{});
}

Run nix develop and zig run main.zig.

[rootbeer]

Fix looks good to me (just a drive-by reviewer). However, because your diff hits File.zig, this PR should probably wait at least until #24329 lands (just to avoid creating merge traffic for it).