Add basic tcp socket test

crates/lb/src/net.rs

@@ -124,7 +124,11 @@ impl lb_netlib {
     }
 
     extern "Lua-C" fn __parse_skaddr(&self, addr: &str) -> Result<lb_socketaddr> {
-        Ok(addr.parse()?)
+        Ok(if let Ok(addr) = addr.parse() {
+            SocketAddr::new(addr, 0).into() // default port 0
+        } else {
+            addr.parse::<SocketAddr>()?.into()
+        })
     }
 
     /// Creates a new TCP socket configured for IPv4.