diff --git a/src/api.rs b/src/api.rs
index 1ea0d8d..bf035ac 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -36,8 +36,9 @@ pub unsafe extern "C" fn over_tls_client_run(
     ctx: *mut c_void,
 ) -> c_int {
     log::set_max_level(verbosity.into());
-    log::set_boxed_logger(Box::<crate::dump_logger::DumpLogger>::default()).unwrap();
-
+    if let Err(err) = log::set_boxed_logger(Box::<crate::dump_logger::DumpLogger>::default()) {
+        log::info!("failed to set logger, error={:?}", err);
+    }
     _over_tls_client_run(config_path, callback, ctx)
 }
 
@@ -61,12 +62,8 @@ unsafe fn _over_tls_client_run(
     let block = || -> Result<()> {
         let config_path = std::ffi::CStr::from_ptr(config_path).to_str()?;
 
-        let cb = |addr: SocketAddr| {
-            log::trace!("Listening on {}", addr);
-            let port = addr.port();
-            unsafe {
-                ccb.call(port as c_int);
-            }
+        let cb = |addr: SocketAddr| unsafe {
+            ccb.call(addr.port() as _);
         };
 
         let mut config = crate::config::Config::from_config_file(config_path)?;
diff --git a/src/bin/overtls.rs b/src/bin/overtls.rs
index 172d77d..571ec75 100644
--- a/src/bin/overtls.rs
+++ b/src/bin/overtls.rs
@@ -3,6 +3,37 @@ use overtls::{client, config, server, CmdOpt, Error, Result};
 fn main() -> Result<()> {
     let opt = CmdOpt::parse_cmd();
 
+    if opt.c_api {
+        if opt.is_server() {
+            return Err(Error::from("C API is not supported for server"));
+        }
+
+        // Test the C API usage
+        let config_path_str = opt.config.as_path().to_string_lossy().into_owned();
+        let c_string = std::ffi::CString::new(config_path_str).unwrap();
+        let config_path: *const std::os::raw::c_char = c_string.as_ptr();
+
+        let join = ctrlc2::set_handler(|| {
+            log::info!("Ctrl-C received, exiting...");
+            unsafe { overtls::over_tls_client_stop() };
+            true
+        })
+        .expect("Error setting Ctrl-C handler");
+
+        unsafe extern "C" fn log_cb(_: overtls::ArgVerbosity, msg: *const std::os::raw::c_char, _ctx: *mut std::os::raw::c_void) {
+            println!("{:?}", unsafe { std::ffi::CStr::from_ptr(msg).to_str() });
+        }
+        unsafe { overtls::overtls_set_log_callback(Some(log_cb), std::ptr::null_mut()) };
+
+        unsafe extern "C" fn port_cb(port: i32, _ctx: *mut std::os::raw::c_void) {
+            log::info!("Listening on {}", port);
+        }
+        unsafe { overtls::over_tls_client_run(config_path, opt.verbosity, Some(port_cb), std::ptr::null_mut()) };
+
+        join.join().unwrap();
+        return Ok(());
+    }
+
     dotenvy::dotenv().ok();
 
     let level = format!("{}={:?}", module_path!(), opt.verbosity);
diff --git a/src/cmdopt.rs b/src/cmdopt.rs
index 65f6b67..6c15944 100644
--- a/src/cmdopt.rs
+++ b/src/cmdopt.rs
@@ -100,6 +100,10 @@ pub struct CmdOpt {
     /// Generate QR code for client.
     #[arg(short, long)]
     pub qrcode: bool,
+
+    /// Use C API for client.
+    #[arg(long)]
+    pub c_api: bool,
 }
 
 impl CmdOpt {
diff --git a/src/dump_logger.rs b/src/dump_logger.rs
index ec1500c..2f6a800 100644
--- a/src/dump_logger.rs
+++ b/src/dump_logger.rs
@@ -5,7 +5,7 @@ use std::{
 };
 
 lazy_static::lazy_static! {
-    pub static ref DUMP_CALLBACK: Mutex<Option<DumpCallback>> = Mutex::new(None);
+    static ref DUMP_CALLBACK: Mutex<Option<DumpCallback>> = Mutex::new(None);
 }
 
 /// # Safety
@@ -20,7 +20,7 @@ pub unsafe extern "C" fn overtls_set_log_callback(
 }
 
 #[derive(Clone)]
-pub struct DumpCallback(Option<unsafe extern "C" fn(ArgVerbosity, *const c_char, *mut c_void)>, *mut c_void);
+struct DumpCallback(Option<unsafe extern "C" fn(ArgVerbosity, *const c_char, *mut c_void)>, *mut c_void);
 
 impl DumpCallback {
     unsafe fn call(self, dump_level: ArgVerbosity, info: *const c_char) {
@@ -34,7 +34,7 @@ unsafe impl Send for DumpCallback {}
 unsafe impl Sync for DumpCallback {}
 
 #[derive(Debug, Clone, PartialEq, Eq, Default)]
-pub struct DumpLogger {}
+pub(crate) struct DumpLogger;
 
 impl log::Log for DumpLogger {
     fn enabled(&self, metadata: &log::Metadata) -> bool {
diff --git a/src/lib.rs b/src/lib.rs
index 31dab80..ecc8076 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -15,9 +15,11 @@ pub(crate) mod udprelay;
 pub(crate) mod webapi;
 pub(crate) mod weirduri;
 
+pub use api::{over_tls_client_run, over_tls_client_stop};
 use base64_wrapper::{base64_decode, base64_encode, Base64Engine};
 use bytes::BytesMut;
 pub use cmdopt::{ArgVerbosity, CmdOpt, Role};
+pub use dump_logger::overtls_set_log_callback;
 pub use error::{Error, Result};
 use socks5_impl::protocol::{Address, StreamOperation};
 pub use tokio_util::sync::CancellationToken;