use a more compatible approach for non-blocking sockets.

(instead of a linux-only flag)

example.zig

@@ -5,25 +5,58 @@ const zanzara = @import("src/zanzara.zig");
 const DefaultClient = zanzara.mqtt4.DefaultClient;
 const Subscribe = zanzara.mqtt4.packet.Subscribe;
 
+const TcpConnectToAddressError = std.posix.SocketError || std.posix.ConnectError;
+
+fn tcpConnectToAddressNonBlock(address: net.Address) TcpConnectToAddressError!net.Stream {
+    const sock_flags = std.posix.SOCK.STREAM | std.posix.SOCK.NONBLOCK;
+    const sockfd = try std.posix.socket(address.any.family, sock_flags, std.posix.IPPROTO.TCP);
+    errdefer net.Stream.close(.{ .handle = sockfd });
+
+    std.posix.connect(sockfd, &address.any, address.getOsSockLen()) catch |err| {
+        switch (err) {
+            error.WouldBlock => std.time.sleep(1 * std.time.ns_per_s), // Todo: handle this better
+            else => return err,
+        }
+    };
+
+    return net.Stream{ .handle = sockfd };
+}
+
+fn tcpConnectToHostNonBlock(allocator: std.mem.Allocator, name: []const u8, port: u16) net.TcpConnectToHostError!net.Stream {
+    const list = try net.getAddressList(allocator, name, port);
+    defer list.deinit();
+
+    if (list.addrs.len == 0) return error.UnknownHostName;
+
+    for (list.addrs) |addr| {
+        return tcpConnectToAddressNonBlock(addr) catch |err| switch (err) {
+            error.ConnectionRefused => {
+                continue;
+            },
+            else => return err,
+        };
+    }
+    return std.posix.ConnectError.ConnectionRefused;
+}
+
 pub fn main() !void {
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     const allocator = gpa.allocator();
 
-    const stream = try net.tcpConnectToHost(allocator, "mqtt.eclipseprojects.io", 1883);
+    const stream = try tcpConnectToHost(allocator, "mqtt.eclipseprojects.io", 1883);
     const socket = stream.handle;
     const writer = stream.writer();
 
-    var mqtt_buf: [2048]u8 = undefined;
+    var mqtt_buf: [32 * 2048]u8 = undefined;
+    var client = try DefaultClient.init(mqtt_buf[0 .. 1024 * 32], mqtt_buf[1024 * 32 ..]);
 
-    var client = try DefaultClient.init(mqtt_buf[0..1024], mqtt_buf[1024..]);
     // See ConnectOpts for additional options
     try client.connect(.{ .client_id = "zanzara" });
 
-    var read_buf: [2048]u8 = undefined;
+    var read_buf: [32 * 2048]u8 = undefined;
 
     while (true) {
-        // We use os.MSG.DONTWAIT so the socket returns WouldBlock if no data is present
-        const bytes = std.posix.recv(socket, &read_buf, std.posix.MSG.DONTWAIT) catch |err|
+        const bytes = std.posix.recv(socket, &read_buf, 0) catch |err|
             if (err == error.WouldBlock) 0 else return err;
         var rest = read_buf[0..bytes];
         while (true) {