feat: Add sal-net package to workspace

- Add new sal-net package to the workspace.
- Update MONOREPO_CONVERSION_PLAN.md to reflect the
  addition of the sal-net package and mark it as
  production-ready.
- Add Cargo.toml and README.md for the sal-net package.

net/tests/tcp_tests.rs

@@ -0,0 +1,179 @@
+use sal_net::TcpConnector;
+use std::net::{IpAddr, Ipv4Addr};
+use std::time::Duration;
+use tokio::net::TcpListener;
+
+#[tokio::test]
+async fn test_tcp_connector_new() {
+    let connector = TcpConnector::new();
+
+    // Test that the connector can actually perform operations
+    // Use a port that should be closed to verify the connector works
+    let result = connector
+        .check_port(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 65534)
+        .await;
+    assert!(result.is_ok());
+    assert!(!result.unwrap()); // Port should be closed
+}
+
+#[tokio::test]
+async fn test_tcp_connector_with_timeout() {
+    let timeout = Duration::from_millis(100); // Short timeout for testing
+    let connector = TcpConnector::with_timeout(timeout);
+
+    // Test that the custom timeout is actually used by trying to connect to a non-routable IP
+    // This should timeout quickly with our short timeout
+    let start = std::time::Instant::now();
+    let result = connector
+        .check_port(IpAddr::V4(Ipv4Addr::new(10, 255, 255, 1)), 80)
+        .await;
+    let elapsed = start.elapsed();
+
+    assert!(result.is_ok());
+    assert!(!result.unwrap()); // Should timeout and return false
+    assert!(elapsed < Duration::from_secs(2)); // Should timeout much faster than default
+}
+
+#[tokio::test]
+async fn test_tcp_connector_default() {
+    let connector = TcpConnector::default();
+
+    // Test that default constructor creates a working connector
+    // Verify it behaves the same as TcpConnector::new()
+    let result = connector
+        .check_port(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 65534)
+        .await;
+    assert!(result.is_ok());
+    assert!(!result.unwrap()); // Port should be closed
+
+    // Test that it can also ping (basic functionality test)
+    let ping_result = connector.ping("127.0.0.1").await;
+    assert!(ping_result.is_ok()); // Should not error, regardless of ping success
+}
+
+#[tokio::test]
+async fn test_check_port_open() {
+    // Start a test server
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let addr = listener.local_addr().unwrap();
+
+    // Keep the listener alive in a background task
+    let _handle = tokio::spawn(async move {
+        loop {
+            if let Ok((stream, _)) = listener.accept().await {
+                drop(stream); // Immediately close the connection
+            }
+        }
+    });
+
+    // Give the server a moment to start
+    tokio::time::sleep(Duration::from_millis(10)).await;
+
+    let connector = TcpConnector::new();
+    let result = connector.check_port(addr.ip(), addr.port()).await;
+
+    assert!(result.is_ok());
+    assert!(result.unwrap()); // Port should be open
+}
+
+#[tokio::test]
+async fn test_check_port_closed() {
+    let connector = TcpConnector::new();
+
+    // Use a port that's very unlikely to be open
+    let result = connector
+        .check_port(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 65534)
+        .await;
+
+    assert!(result.is_ok());
+    assert!(!result.unwrap()); // Port should be closed
+}
+
+#[tokio::test]
+async fn test_check_port_timeout() {
+    let connector = TcpConnector::with_timeout(Duration::from_millis(1));
+
+    // Use a non-routable IP to trigger timeout
+    let result = connector
+        .check_port(IpAddr::V4(Ipv4Addr::new(10, 255, 255, 1)), 80)
+        .await;
+
+    assert!(result.is_ok());
+    assert!(!result.unwrap()); // Should timeout and return false
+}
+
+#[tokio::test]
+async fn test_check_multiple_ports() {
+    // Start test servers on multiple ports
+    let listener1 = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let addr1 = listener1.local_addr().unwrap();
+    let listener2 = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let addr2 = listener2.local_addr().unwrap();
+
+    // Keep listeners alive
+    let _handle1 = tokio::spawn(async move {
+        loop {
+            if let Ok((stream, _)) = listener1.accept().await {
+                drop(stream);
+            }
+        }
+    });
+    let _handle2 = tokio::spawn(async move {
+        loop {
+            if let Ok((stream, _)) = listener2.accept().await {
+                drop(stream);
+            }
+        }
+    });
+
+    tokio::time::sleep(Duration::from_millis(10)).await;
+
+    let connector = TcpConnector::new();
+    let ports = vec![addr1.port(), addr2.port(), 65533]; // Two open, one closed
+    let results = connector.check_ports(addr1.ip(), &ports).await;
+
+    assert!(results.is_ok());
+    let results = results.unwrap();
+    assert_eq!(results.len(), 3);
+
+    // First two should be open, last should be closed
+    assert!(results[0].1); // addr1.port() should be open
+    assert!(results[1].1); // addr2.port() should be open
+    assert!(!results[2].1); // 65533 should be closed
+}
+
+#[tokio::test]
+async fn test_ping_localhost() {
+    let connector = TcpConnector::new();
+
+    // Ping localhost - should work on most systems
+    let result = connector.ping("localhost").await;
+
+    // Note: This might fail in some environments (containers, etc.)
+    // so we just verify the function doesn't panic and returns a boolean result
+    assert!(result.is_ok());
+}
+
+#[tokio::test]
+async fn test_ping_invalid_host() {
+    let connector = TcpConnector::new();
+
+    // Ping an invalid hostname
+    let result = connector
+        .ping("this-host-definitely-does-not-exist-12345")
+        .await;
+
+    assert!(result.is_ok());
+    assert!(!result.unwrap()); // Should fail to ping invalid host
+}
+
+#[tokio::test]
+async fn test_ping_timeout() {
+    let connector = TcpConnector::with_timeout(Duration::from_millis(1));
+
+    // Use a non-routable IP to trigger timeout
+    let result = connector.ping("10.255.255.1").await;
+
+    assert!(result.is_ok());
+    // Result could be true or false depending on system, but shouldn't panic
+}