diff --git a/include/ftp/detail/socket.hpp b/include/ftp/detail/socket.hpp
index 36fc597..fc45f92 100644
--- a/include/ftp/detail/socket.hpp
+++ b/include/ftp/detail/socket.hpp
@@ -41,7 +41,7 @@ class socket : public socket_base
 
     void connect(const boost::asio::ip::tcp::endpoint & ep, boost::system::error_code & ec) override;
 
-    bool is_connected() const override;
+    [[nodiscard]] bool is_connected() const override;
 
     std::size_t write(const char *buf, std::size_t size, boost::system::error_code & ec) override;
 
@@ -55,13 +55,13 @@ class socket : public socket_base
 
     void close(boost::system::error_code & ec) override;
 
-    boost::asio::ip::tcp::endpoint local_endpoint(boost::system::error_code & ec) const override;
+    [[nodiscard]] boost::asio::ip::tcp::endpoint local_endpoint(boost::system::error_code & ec) const override;
 
-    boost::asio::ip::tcp::endpoint remote_endpoint(boost::system::error_code & ec) const override;
+    [[nodiscard]] boost::asio::ip::tcp::endpoint remote_endpoint(boost::system::error_code & ec) const override;
 
-    boost::asio::ip::tcp::socket::executor_type get_executor() override;
+    [[nodiscard]] boost::asio::ip::tcp::socket::executor_type get_executor() override;
 
-    boost::asio::ip::tcp::socket & get_socket() override;
+    [[nodiscard]] boost::asio::ip::tcp::socket & get_socket() override;
 
 private:
     boost::asio::ip::tcp::socket socket_;
diff --git a/include/ftp/detail/socket_base.hpp b/include/ftp/detail/socket_base.hpp
index 8e9dd50..8e06d02 100644
--- a/include/ftp/detail/socket_base.hpp
+++ b/include/ftp/detail/socket_base.hpp
@@ -41,7 +41,7 @@ class socket_base
 
     virtual void connect(const boost::asio::ip::tcp::endpoint & ep, boost::system::error_code & ec) = 0;
 
-    virtual bool is_connected() const = 0;
+    [[nodiscard]] virtual bool is_connected() const = 0;
 
     virtual std::size_t write(const char *buf, std::size_t size, boost::system::error_code & ec) = 0;
 
@@ -55,14 +55,14 @@ class socket_base
 
     virtual void close(boost::system::error_code & ec) = 0;
 
-    virtual boost::asio::ip::tcp::endpoint local_endpoint(boost::system::error_code & ec) const = 0;
+    [[nodiscard]] virtual boost::asio::ip::tcp::endpoint local_endpoint(boost::system::error_code & ec) const = 0;
 
-    virtual boost::asio::ip::tcp::endpoint remote_endpoint(boost::system::error_code & ec) const = 0;
+    [[nodiscard]] virtual boost::asio::ip::tcp::endpoint remote_endpoint(boost::system::error_code & ec) const = 0;
 
-    virtual boost::asio::ip::tcp::socket::executor_type get_executor() = 0;
+    [[nodiscard]] virtual boost::asio::ip::tcp::socket::executor_type get_executor() = 0;
 
     // TODO: Remove.
-    virtual boost::asio::ip::tcp::socket & get_socket() = 0;
+    [[nodiscard]] virtual boost::asio::ip::tcp::socket & get_socket() = 0;
 
     virtual ~socket_base() = default;
 
@@ -125,12 +125,14 @@ class socket_base
     }
 
     template<typename SocketType>
+    [[nodiscard]]
     boost::asio::ip::tcp::endpoint local_endpoint(const SocketType & socket, boost::system::error_code & ec) const
     {
         return socket.local_endpoint(ec);
     }
 
     template<typename SocketType>
+    [[nodiscard]]
     boost::asio::ip::tcp::endpoint remote_endpoint(const SocketType & socket, boost::system::error_code & ec) const
     {
         return socket.remote_endpoint(ec);