Receiving fd with Zig!
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208
zig-impl/misc/rcv-fd.zig
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208
zig-impl/misc/rcv-fd.zig
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const std = @import("std");
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const testing = std.testing;
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const net = std.net;
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const fmt = std.fmt;
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const os = std.os;
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const mem = std.mem;
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const print = std.debug.print;
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const Cmsghdr = @import("./cmsghdr.zig").Cmsghdr;
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const system = std.os.system;
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const socket_t = std.os.socket_t;
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const msghdr = system.msghdr;
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const builtin = @import("builtin");
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const windows = std.os.windows;
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const errno = std.os.errno;
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const unexpectedErrno = std.os.unexpectedErrno;
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const SendMsgError = std.os.SendMsgError;
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pub fn recvmsg(
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/// The file descriptor of the sending socket.
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sockfd: socket_t,
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/// Message header and iovecs
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msg: msghdr,
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flags: u32,
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) SendMsgError!usize {
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while (true) {
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var m = msg;
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const rc = system.recvmsg(sockfd, @ptrCast(*std.x.os.Socket.Message, &m), @intCast(c_int, flags));
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if (builtin.os.tag == .windows) {
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if (rc == windows.ws2_32.SOCKET_ERROR) {
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switch (windows.ws2_32.WSAGetLastError()) {
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.WSAEACCES => return error.AccessDenied,
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.WSAEADDRNOTAVAIL => return error.AddressNotAvailable,
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.WSAECONNRESET => return error.ConnectionResetByPeer,
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.WSAEMSGSIZE => return error.MessageTooBig,
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.WSAENOBUFS => return error.SystemResources,
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.WSAENOTSOCK => return error.FileDescriptorNotASocket,
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.WSAEAFNOSUPPORT => return error.AddressFamilyNotSupported,
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.WSAEDESTADDRREQ => unreachable, // A destination address is required.
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.WSAEFAULT => unreachable, // The lpBuffers, lpTo, lpOverlapped, lpNumberOfBytesSent, or lpCompletionRoutine parameters are not part of the user address space, or the lpTo parameter is too small.
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.WSAEHOSTUNREACH => return error.NetworkUnreachable,
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// TODO: WSAEINPROGRESS, WSAEINTR
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.WSAEINVAL => unreachable,
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.WSAENETDOWN => return error.NetworkSubsystemFailed,
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.WSAENETRESET => return error.ConnectionResetByPeer,
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.WSAENETUNREACH => return error.NetworkUnreachable,
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.WSAENOTCONN => return error.SocketNotConnected,
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.WSAESHUTDOWN => unreachable, // The socket has been shut down; it is not possible to WSASendTo on a socket after shutdown has been invoked with how set to SD_SEND or SD_BOTH.
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.WSAEWOULDBLOCK => return error.WouldBlock,
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.WSANOTINITIALISED => unreachable, // A successful WSAStartup call must occur before using this function.
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else => |err| return windows.unexpectedWSAError(err),
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}
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} else {
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return @intCast(usize, rc);
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}
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} else {
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switch (errno(rc)) {
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.SUCCESS => return @intCast(usize, rc),
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.ACCES => return error.AccessDenied,
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.AGAIN => return error.WouldBlock,
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.ALREADY => return error.FastOpenAlreadyInProgress,
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.BADF => unreachable, // always a race condition
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.CONNRESET => return error.ConnectionResetByPeer,
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.DESTADDRREQ => unreachable, // The socket is not connection-mode, and no peer address is set.
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.FAULT => unreachable, // An invalid user space address was specified for an argument.
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.INTR => continue,
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.INVAL => unreachable, // Invalid argument passed.
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.ISCONN => unreachable, // connection-mode socket was connected already but a recipient was specified
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.MSGSIZE => return error.MessageTooBig,
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.NOBUFS => return error.SystemResources,
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.NOMEM => return error.SystemResources,
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.NOTSOCK => unreachable, // The file descriptor sockfd does not refer to a socket.
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.OPNOTSUPP => unreachable, // Some bit in the flags argument is inappropriate for the socket type.
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.PIPE => return error.BrokenPipe,
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.AFNOSUPPORT => return error.AddressFamilyNotSupported,
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.LOOP => return error.SymLinkLoop,
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.NAMETOOLONG => return error.NameTooLong,
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.NOENT => return error.FileNotFound,
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.NOTDIR => return error.NotDir,
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.HOSTUNREACH => return error.NetworkUnreachable,
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.NETUNREACH => return error.NetworkUnreachable,
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.NOTCONN => return error.SocketNotConnected,
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.NETDOWN => return error.NetworkSubsystemFailed,
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else => |err| return unexpectedErrno(err),
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}
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}
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}
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}
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fn disconnect(stream: *net.StreamServer) void { stream.close(); }
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fn server_init() net.StreamServer {
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// no reuse_address and default kernel_backlog
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return net.StreamServer.init(.{});
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}
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fn waiting_for_connection(stream: *net.StreamServer
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, path: []const u8) !net.StreamServer.Connection {
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var address = try net.Address.initUnix(path);
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try stream.listen(address);
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return stream.accept();
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}
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fn remove_unix_socket(path: []const u8) void {
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std.fs.deleteFileAbsolute(path) catch |err| switch(err) {
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else => { print("error: {}\n", .{err}); }
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};
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}
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const SCM_RIGHTS: c_int = 1;
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fn send_msg(sock: os.socket_t, msg: []const u8, fd: os.fd_t) void {
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var iov = [_]os.iovec_const{
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.{
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.iov_base = msg.ptr,
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.iov_len = msg.len,
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},
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};
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var cmsg = Cmsghdr(os.fd_t).init(.{
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.level = os.SOL.SOCKET,
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.@"type" = SCM_RIGHTS,
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.data = fd,
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});
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const len = os.sendmsg(sock, .{
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.name = undefined,
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.namelen = 0,
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.iov = &iov,
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.iovlen = iov.len,
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.control = &cmsg,
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.controllen = @sizeOf(@TypeOf(cmsg)),
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.flags = 0,
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}, 0) catch |err| {
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print("error sendmsg failed with {s}", .{@errorName(err)});
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return;
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};
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if (len != msg.len) {
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// we don't have much choice but to exit here
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// log.err(@src(), "expected sendmsg to return {} but got {}", .{msg.len, len});
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print("expected sendmsg to return {} but got {}", .{msg.len, len});
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os.exit(0xff);
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}
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}
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fn receive_msg(sock: os.socket_t) !os.fd_t {
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var buffer: [100]u8 = undefined;
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var iov = [1]os.iovec{
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.{
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.iov_base = buffer[0..],
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.iov_len = buffer.len,
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},
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};
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var cmsg = Cmsghdr(os.fd_t).init(.{
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.level = os.SOL.SOCKET,
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.@"type" = SCM_RIGHTS,
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.data = undefined,
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});
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var msg: std.os.msghdr = .{
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.name = undefined,
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.namelen = 0,
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.iov = &iov,
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.iovlen = iov.len,
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.control = &cmsg,
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.controllen = @sizeOf(@TypeOf(cmsg)),
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.flags = 0,
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};
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const len = recvmsg(sock, msg, 0) catch |err| {
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print("error sendmsg failed with {s}", .{@errorName(err)});
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return 0;
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};
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print("received {} bytes, fd is {}\n", .{len, @as(i32, cmsg.dataPtr().*)});
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print("iov base {s}\n", .{iov[0].iov_base[0..iov[0].iov_len - 1]});
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return @as(i32, cmsg.dataPtr().*);
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}
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fn add_line_from_fd(fd: i32) !void {
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// var f = std.fs.File {.handle = fd};
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// defer f.close();
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_ = try std.os.write(fd, "hello this is another line\n");
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std.os.close(fd);
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}
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pub fn main() !u8 {
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var path = "/tmp/.TEST_USOCK";
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print("Init UNIX server to {s}...\n", .{path});
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var stream = server_init();
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defer stream.deinit();
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print("Waiting for a connection...\n", .{});
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var connection = try waiting_for_connection(&stream, path);
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defer remove_unix_socket(path);
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print("Someone is connected! Receiving a file descriptor...\n", .{});
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var fd = try receive_msg(connection.stream.handle);
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print("FD received, writing a line into the file...\n", .{});
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try add_line_from_fd(fd);
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print("Disconnection...\n", .{});
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disconnect(&stream);
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print("Disconnected!\n", .{});
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return 0;
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}
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