diff --git a/src/socket_proxy/__main__.py b/src/socket_proxy/__main__.py
index 0dc6aae..69476a1 100644
--- a/src/socket_proxy/__main__.py
+++ b/src/socket_proxy/__main__.py
@@ -410,7 +410,7 @@ def parse_args(args: Tuple[str] = None) -> None:
 def run_client(no_curses: bool) -> None:
     for arg in ["ca", "connect", "dst"]:
         if not getattr(base.config, arg, False):
-            _logger.critical("Missing --%s argument", arg)
+            _logger.critical(f"Missing --{arg} argument")
             sys.exit(1)
 
     cls = TunnelClient if no_curses else GUIClient
@@ -430,7 +430,7 @@ def run_client(no_curses: bool) -> None:
 def run_server() -> None:
     for arg in ["cert", "key"]:
         if not getattr(base.config, arg, False):
-            _logger.critical("Missing --%s argument", arg)
+            _logger.critical(f"Missing --{arg} argument")
             sys.exit(1)
 
     server = ProxyServer(
diff --git a/src/socket_proxy/api.py b/src/socket_proxy/api.py
index e38af4f..4fe570e 100644
--- a/src/socket_proxy/api.py
+++ b/src/socket_proxy/api.py
@@ -83,7 +83,7 @@ async def start_api(self) -> None:
         extras = sorted(filter(None, extras))
         extras = f"[{','.join(extras)}]" if extras else ""
 
-        _logger.info("Starting API on %s:%s %s", self.api_host, self.api_port, extras)
+        _logger.info(f"Starting API on {self.api_host}:{self.api_port} {extras}")
         self.api = web.Application()
         self.api.add_routes(
             [
diff --git a/src/socket_proxy/base.py b/src/socket_proxy/base.py
index 0ee6038..5153452 100644
--- a/src/socket_proxy/base.py
+++ b/src/socket_proxy/base.py
@@ -76,7 +76,7 @@ class ProtocolType(enum.IntEnum):
     TCP = 0x01
     HTTP = 0x02
 
-    def __str__(self):
+    def __str__(self) -> str:
         return {
             ProtocolType.TCP: "TCP",
             ProtocolType.HTTP: "HTTP",
diff --git a/src/socket_proxy/proxy.py b/src/socket_proxy/proxy.py
index 3562034..3ddc529 100644
--- a/src/socket_proxy/proxy.py
+++ b/src/socket_proxy/proxy.py
@@ -126,11 +126,8 @@ def generate_token(self, hotp: bool = False) -> str:
 
         token = str(uuid.uuid4())
         self.tokens[token] = None if hotp else datetime.now()
-        _logger.info(
-            "Generated authentication token %s [%s]",
-            token,
-            "hotp" if hotp else "totp",
-        )
+        ttype = "hotp" if hotp else "totp"
+        _logger.info(f"Generated authentication token {token} [{ttype}]")
         self.event.send_nowait(msg="token_generate", token=token, hotp=bool(hotp))
         self._persist_state()
         return token
diff --git a/src/socket_proxy/tunnel.py b/src/socket_proxy/tunnel.py
index e786928..f92e50a 100644
--- a/src/socket_proxy/tunnel.py
+++ b/src/socket_proxy/tunnel.py
@@ -54,7 +54,7 @@ def token(self) -> str:
     def uuid(self) -> str:
         return self.tunnel.uuid
 
-    def get_config_dict(self):
+    def get_config_dict(self) -> dict:
         """Return the configuration as a dictionary used in the API or client"""
         return {
             "bantime": self.bantime or None,
@@ -104,10 +104,10 @@ def get_state_dict(self) -> dict:
         }
 
     def info(self, msg: str, *args) -> None:
-        _logger.info("Tunnel %s " + msg, self.uuid, *args)
+        _logger.info(f"Tunnel {self.uuid} {msg}", *args)
 
     def error(self, msg: str, *args) -> None:
-        _logger.error("Tunnel %s " + msg, self.uuid, *args)
+        _logger.error(f"Tunnel {self.uuid} {msg}", *args)
 
     def add(self, client: Connection) -> None:
         if client.token in self.clients:
@@ -147,7 +147,7 @@ async def _disconnect_client(self, token: bytes) -> None:
             # Store the traffic information from the disconnecting clients
             self.bytes_in += client.bytes_in
             self.bytes_out += client.bytes_out
-            _logger.info("Client %s disconnected", token.hex())
+            _logger.info(f"Client {token.hex()} disconnected")
             await client.close()
 
     async def idle(self) -> None:
diff --git a/src/socket_proxy/tunnel_client.py b/src/socket_proxy/tunnel_client.py
index 05bc9dd..53ce2a9 100644
--- a/src/socket_proxy/tunnel_client.py
+++ b/src/socket_proxy/tunnel_client.py
@@ -63,7 +63,7 @@ async def idle(self) -> None:
         self.last_ping = time.time()
         await self.tunnel.tun_write(package.PingPackage(self.last_ping))
 
-    def _check_alive(self):
+    def _check_alive(self) -> bool:
         """Check if the connection is alive using the last ping"""
 
         if self.last_ping is None or self.last_pong is None:
@@ -76,7 +76,7 @@ def _check_alive(self):
 
     async def _client_loop(self, client: Connection) -> None:
         """This is the main client loop"""
-        _logger.info("Client %s connected", client.token.hex())
+        _logger.info(f"Client {client.token.hex()} connected")
         while True:
             data = await client.read(self.chunk_size)
             if not data:
@@ -168,7 +168,7 @@ async def _handle(self) -> bool:
 
         # Something unexpected happened
         if pkg is not None:
-            self.error("invalid package: %s", pkg)
+            self.error(f"invalid package: {pkg}")
             return await super()._handle()
 
         return await super()._handle()
@@ -190,8 +190,8 @@ async def loop(self) -> None:
         self.tunnel = await Connection.connect(self.host, self.port, ssl=self.sc)
         ssl_obj = self.tunnel.writer.get_extra_info("ssl_object")
         extra = f" [{ssl_obj.version()}]" if ssl_obj else ""
-        _logger.info("Tunnel %s:%s connected%s", self.host, self.port, extra)
-        _logger.info("Forwarding to %s:%s", self.dst_host, self.dst_port)
+        _logger.info(f"Tunnel {self.host}:{self.port} connected{extra}")
+        _logger.info(f"Forwarding to {self.dst_host}:{self.dst_port}")
 
         if self.api_port:
             asyncio.create_task(self.start_api())
@@ -214,7 +214,7 @@ async def loop(self) -> None:
         finally:
             self.running = False
             await self.stop()
-            _logger.info("Tunnel %s:%s closed", self.host, self.port)
+            _logger.info(f"Tunnel {self.host}:{self.port} closed")
 
     def start(self) -> None:
         """Start the client and the event loop"""
diff --git a/src/socket_proxy/tunnel_gui.py b/src/socket_proxy/tunnel_gui.py
index f3ecfbb..097af9b 100644
--- a/src/socket_proxy/tunnel_gui.py
+++ b/src/socket_proxy/tunnel_gui.py
@@ -4,7 +4,7 @@
 from logging.handlers import QueueHandler
 from typing import List
 
-from .base import LOG_FORMAT, InternetType
+from .base import LOG_FORMAT, InternetType, IPvXAddress
 from .tunnel_client import TunnelClient
 from .utils import format_transfer
 
@@ -33,6 +33,11 @@ def get_dimension(self) -> None:
         """Get the dimensions of the current window"""
         self.height, self.width = self.scr.getmaxyx()
 
+    # pylint: disable=W0613,R0201
+    def fmt_port(self, ip_type: InternetType, ip: IPvXAddress, port: int) -> str:
+        """Format an address"""
+        return f"{ip}:{port}" if ip else str(port)
+
     def _draw(self) -> None:
         """Draw all GUI elements"""
         self.scr.clear()
@@ -115,7 +120,8 @@ def _draw_log(self) -> None:
         win.refresh()
         return win
 
-    def _draw_lines(self, win, lines: List[str]) -> None:  # pylint: disable=R0201
+    # disable: pylint=R0201
+    def _draw_lines(self, win: curses.window, lines: List[str]) -> None:
         """Draw multiple lines in a window with some border"""
         h, w = [k - 2 for k in win.getmaxyx()]
         for y, line in enumerate(lines[:h]):
@@ -127,7 +133,7 @@ async def _handle(self) -> bool:
         self._draw()
         return await super()._handle()
 
-    def _gui(self, scr) -> None:
+    def _gui(self, scr: curses.window) -> None:
         """Configure the main screen"""
         self.scr = scr
         curses.noecho()
diff --git a/src/socket_proxy/tunnel_server.py b/src/socket_proxy/tunnel_server.py
index ea0448d..cbeb78e 100644
--- a/src/socket_proxy/tunnel_server.py
+++ b/src/socket_proxy/tunnel_server.py
@@ -58,7 +58,7 @@ async def idle(self) -> None:
         for ip, ban in list(self.connections.items()):
             if ban.first < dt:
                 self.connections.pop(ip)
-                _logger.info("Connection number of %s resetted", ip)
+                _logger.info(f"Connection number of {ip} resetted")
 
     async def _client_accept(
         self,
@@ -76,7 +76,7 @@ async def _client_accept(
             writer.close()
             await writer.wait_closed()
 
-            _logger.info("Connection from %s blocked", ip)
+            _logger.info(f"Connection from {ip} blocked")
             await self.event.send(msg="client_blocked", tunnel=self.uuid, ip=str(ip))
             return
 
@@ -86,7 +86,7 @@ async def _client_accept(
         client = Connection(reader, writer, self.protocol, utils.generate_token())
         self.add(client)
 
-        _logger.info("Client %s connected on %s:%s", client.uuid, host, port)
+        _logger.info(f"Client {client.uuid} connected on {host}:{port}")
         await self.event.send(
             msg="client_connect",
             tunnel=self.uuid,
@@ -149,7 +149,7 @@ async def _client_loop(self) -> None:
 
         # Initialize the tunnel by sending the appropiate data
         out = " ".join(sorted(f"{host}:{port}" for host, port in self.addr))
-        self.info("Listen on %s", out)
+        self.info(f"Listen on {out}")
 
         addr = [(base.InternetType.from_ip(ip), ip, port) for ip, port in self.addr]
         pkg = package.InitPackage(self.token, addr, self.domain)
@@ -168,10 +168,10 @@ async def _handle(self) -> bool:
                 self.error(f"Disabled protocol {self.protocol.name}")
                 return False
 
-            self.info("Using protocol: %s", self.protocol.name)
+            self.info(f"Using protocol: {self.protocol.name}")
 
             if self.protocol != base.ProtocolType.TCP:
-                self.info("Reachable with domain: %s", self.domain)
+                self.info(f"Reachable with domain: {self.domain}")
                 pkg = package.InitPackage(self.token, [], self.domain)
                 await self.tunnel.tun_write(pkg)
             elif not await self._open_server():
@@ -199,7 +199,7 @@ async def _handle(self) -> bool:
         if isinstance(pkg, package.ClientDataPackage):
             # Check for valid tokens
             if pkg.token not in self:
-                self.error("Invalid client token: %s", pkg.token)
+                self.error(f"Invalid client token: {pkg.token}")
                 return False
 
             conn = self[pkg.token]
@@ -208,7 +208,7 @@ async def _handle(self) -> bool:
 
         # Invalid package means to close the connection
         if pkg is not None:
-            self.error("Invalid package: %s", pkg)
+            self.error(f"Invalid package: {pkg}")
             return await super()._handle()
 
         return await super()._handle()
@@ -227,7 +227,7 @@ async def loop(self) -> None:
         """Main loop of the proxy tunnel"""
         ssl_obj = self.tunnel.writer.get_extra_info("ssl_object")
         extra = f" [{ssl_obj.version()}]" if ssl_obj else ""
-        self.info("Connected %s:%s%s", self.host, self.port, extra)
+        self.info(f"Connected {self.host}:{self.port}{extra}")
 
         try:
             await self._serve()
diff --git a/src/socket_proxy/utils.py b/src/socket_proxy/utils.py
index 1a5755f..247b420 100644
--- a/src/socket_proxy/utils.py
+++ b/src/socket_proxy/utils.py
@@ -156,14 +156,14 @@ def generate_ssl_context(
         ctx.set_ciphers(ciphers)
 
     # Output debugging
-    _logger.info("CA usage: %s", bool(ca))
-    _logger.info("Certificate: %s", bool(cert))
-    _logger.info("Hostname verification: %s", bool(check_hostname))
+    _logger.info(f"CA usage: {bool(ca)}")
+    _logger.info(f"Certificate: {bool(cert)}")
+    _logger.info(f"Hostname verification: {bool(check_hostname)}")
     # pylint: disable=no-member
-    _logger.info("Minimal TLS Version: %s", ctx.minimum_version.name)
+    _logger.info(f"Minimal TLS Version: {ctx.minimum_version.name}")
 
     ciphers = sorted(c["name"] for c in ctx.get_ciphers())
-    _logger.info("Ciphers: %s", ", ".join(ciphers))
+    _logger.info(f"Ciphers: {', '.join(ciphers)}")
 
     return ctx