diff --git a/DOC.md b/DOC.md
index 3aa93b7..e38f04d 100644
--- a/DOC.md
+++ b/DOC.md
@@ -68,16 +68,10 @@ on the server level.
 ## Device State - Active and Inactive
 To solve this problem, each device can be in exactly two states:
 
-Events can only be sent to active clients.
-Events can only be received from inactive clients.
+Either events are sent or received.
 
-Active denotes that a particular device is controlled by the local pc.
+This ensures that
+- a) Events can never result in a feedback loop.
+- b) As soon as a virtual input enters another client, lan-mouse will stop receiving events,
+which ensures clients can only be controlled directly and not indirectly through other clients.
 
-Any event received from an active device is ignored unless it is a state change request.
-In this case the device is marked as inactive and no further events are sent to the device.
-
-The received events are then processed until a further state change to active
-is requested (when the corresponding layer surface is entered).
-
-**In short:** The invariance "each client either sends or receives events" must
-always be true.
diff --git a/config.toml b/config.toml
index 94b36cf..912da89 100644
--- a/config.toml
+++ b/config.toml
@@ -1,11 +1,11 @@
 port = 42069
 backend = "wlroots"
 
-# [client.right]
+# [right]
 # host_name = "localhost"
 # port = 42068
 
-[client.left]
+[left]
 host_name = "Osmium"
 ip = "192.168.178.114"
 port = 42069
diff --git a/src/client.rs b/src/client.rs
index 022a1a3..bac18c5 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -1,4 +1,4 @@
-use std::net::SocketAddr;
+use std::{net::SocketAddr, error::Error, fmt::Display};
 
 use crate::{config, dns};
 
@@ -35,20 +35,29 @@ pub struct ClientManager {
 
 pub type ClientHandle = u32;
 
+#[derive(Debug)]
+struct ClientConfigError;
+
+impl Display for ClientConfigError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "neither ip nor hostname specified")
+    }
+}
+
+impl Error for ClientConfigError {}
+
 impl ClientManager {
-    fn add_client(&mut self, client: &config::Client, pos: Position) {
+    fn add_client(&mut self, client: &config::Client, pos: Position) -> Result<(), Box<dyn Error>> {
         let ip = match client.ip {
             Some(ip) => ip,
             None => match &client.host_name {
-                Some(host_name) => match dns::resolve(host_name) {
-                    Ok(ip) => ip,
-                    Err(e) => panic!("{}", e),
-                },
-                None => panic!("neither ip nor hostname specified"),
+                Some(host_name) => dns::resolve(host_name)?,
+                None => return Err(Box::new(ClientConfigError{})),
             },
         };
         let addr = SocketAddr::new(ip, client.port.unwrap_or(42069));
         self.register_client(addr, pos);
+        Ok(())
     }
 
     fn new_id(&mut self) -> ClientHandle {
@@ -56,7 +65,7 @@ impl ClientManager {
         self.next_id
     }
 
-    pub fn new(config: &config::Config) -> Self {
+    pub fn new(config: &config::Config) -> Result<Self, Box<dyn Error>> {
 
         let mut client_manager = ClientManager {
             next_id: 0,
@@ -64,25 +73,11 @@ impl ClientManager {
         };
 
         // add clients from config
-        for client in vec![
-            &config.client.left,
-            &config.client.right,
-            &config.client.top,
-            &config.client.bottom,
-        ] {
-            if let Some(client) = client {
-                let pos = match client {
-                    client if Some(client) == config.client.left.as_ref() => Position::Left,
-                    client if Some(client) == config.client.right.as_ref() => Position::Right,
-                    client if Some(client) == config.client.top.as_ref() => Position::Top,
-                    client if Some(client) == config.client.bottom.as_ref() => Position::Bottom,
-                    _ => panic!(),
-                };
-                client_manager.add_client(client, pos);
-            }
+        for (client, pos) in config.clients.iter() {
+            client_manager.add_client(&client, *pos)?;
         }
 
-        client_manager
+        Ok(client_manager)
     }
 
     pub fn register_client(&mut self, addr: SocketAddr, pos: Position) {
diff --git a/src/config.rs b/src/config.rs
index 29ad2fc..9b54d45 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,17 +1,17 @@
 use serde_derive::{Deserialize, Serialize};
+use core::fmt;
 use std::net::IpAddr;
 use std::{error::Error, fs};
+
+use std::env;
 use toml;
 
-#[derive(Serialize, Deserialize, Debug)]
-pub struct Config {
-    pub client: Clients,
-    pub port: Option<u16>,
-    pub backend: Option<String>,
-}
+use crate::client::Position;
 
 #[derive(Serialize, Deserialize, Debug)]
-pub struct Clients {
+pub struct ConfigToml {
+    pub port: Option<u16>,
+    pub backend: Option<String>,
     pub left: Option<Client>,
     pub right: Option<Client>,
     pub top: Option<Client>,
@@ -25,9 +25,94 @@ pub struct Client {
     pub port: Option<u16>,
 }
 
-impl Config {
-    pub fn new(path: &str) -> Result<Config, Box<dyn Error>> {
+#[derive(Debug, Clone)]
+struct MissingParameter {
+    arg: &'static str,
+}
+
+impl fmt::Display for MissingParameter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Missing a parameter for argument: {}", self.arg)
+    }
+}
+
+impl Error for MissingParameter {}
+
+impl ConfigToml {
+    pub fn new(path: &str) -> Result<ConfigToml, Box<dyn Error>> {
         let config = fs::read_to_string(path)?;
         Ok(toml::from_str::<_>(&config)?)
     }
 }
+
+fn find_arg(key: &'static str) -> Result<Option<String>, MissingParameter> {
+    let args: Vec<String> = env::args().collect();
+
+    for (i, arg) in args.iter().enumerate() {
+        if arg != key {
+            continue;
+        }
+        match args.get(i+1) {
+            None => return Err(MissingParameter { arg: key }),
+            Some(arg) => return Ok(Some(arg.clone())),
+        };
+    }
+    Ok(None)
+}
+
+pub struct Config {
+    pub backend: Option<String>,
+    pub port: u16,
+    pub clients: Vec<(Client, Position)>,
+}
+
+impl Config {
+    pub fn new() -> Result<Self, Box<dyn Error>> {
+        let config_path = "config.toml";
+        let config_toml = match ConfigToml::new(config_path) {
+            Err(e) => {
+                eprintln!("config.toml: {e}");
+                eprintln!("Continuing without config file ...");
+                None
+            },
+            Ok(c) => Some(c),
+        };
+
+        let backend = match find_arg("--backend")? {
+            None => match &config_toml {
+                Some(c) => c.backend.clone(),
+                None => None,
+            },
+            backend => backend,
+        };
+
+        const DEFAULT_PORT: u16 = 4242;
+
+        let port = match find_arg("--port")? {
+            Some(port) => port.parse::<u16>()?,
+            None => match &config_toml {
+                Some(c) => c.port.unwrap_or(DEFAULT_PORT),
+                None => DEFAULT_PORT,
+            }
+        };
+
+        let mut clients: Vec<(Client, Position)> = vec![];
+
+        if let Some(config_toml) = config_toml {
+            if let Some(c) = config_toml.right {
+                clients.push((c, Position::Right))
+            }
+            if let Some(c) = config_toml.left {
+                clients.push((c, Position::Left))
+            }
+            if let Some(c) = config_toml.top {
+                clients.push((c, Position::Top))
+            }
+            if let Some(c) = config_toml.bottom {
+                clients.push((c, Position::Bottom))
+            }
+        }
+
+        Ok(Config { backend, clients, port })
+    }
+}
diff --git a/src/consumer.rs b/src/consumer.rs
index 92a3ac5..9a11fe1 100644
--- a/src/consumer.rs
+++ b/src/consumer.rs
@@ -1,4 +1,4 @@
-use std::{thread::{JoinHandle, self}, sync::mpsc::Receiver};
+use std::{thread::{JoinHandle, self}, sync::mpsc::Receiver, error::Error};
 
 #[cfg(unix)]
 use std::env;
@@ -14,11 +14,11 @@ enum Backend {
     Libei,
 }
 
-pub fn start(consume_rx: Receiver<(Event, ClientHandle)>, clients: Vec<Client>, backend: Option<String>) -> JoinHandle<()> {
+pub fn start(consume_rx: Receiver<(Event, ClientHandle)>, clients: Vec<Client>, backend: Option<String>) -> Result<JoinHandle<()>, Box<dyn Error>> {
     #[cfg(windows)]
     let _backend = backend;
 
-    thread::Builder::new()
+    Ok(thread::Builder::new()
         .name("event consumer".into())
         .spawn(move || {
             #[cfg(windows)]
@@ -72,6 +72,5 @@ pub fn start(consume_rx: Receiver<(Event, ClientHandle)>, clients: Vec<Client>,
                     consumer::x11::run(consume_rx, clients);
                 },
             }
-        })
-        .unwrap()
+        })?)
 }
diff --git a/src/event/server.rs b/src/event/server.rs
index 8cbd651..41d4713 100644
--- a/src/event/server.rs
+++ b/src/event/server.rs
@@ -20,13 +20,13 @@ pub struct Server {
 }
 
 impl Server {
-    pub fn new(port: u16) -> Self {
-        let listen_addr = SocketAddr::new("0.0.0.0".parse().unwrap(), port);
+    pub fn new(port: u16) -> Result<Self, Box<dyn Error>> {
+        let listen_addr = SocketAddr::new("0.0.0.0".parse()?, port);
         let sending = Arc::new(AtomicBool::new(false));
-        Server {
+        Ok(Server {
             listen_addr,
             sending,
-        }
+        })
     }
 
     pub fn run(
@@ -36,7 +36,7 @@ impl Server {
         consume_tx: SyncSender<(Event, ClientHandle)>,
     ) -> Result<(JoinHandle<()>, JoinHandle<()>), Box<dyn Error>> {
         let udp_socket = UdpSocket::bind(self.listen_addr)?;
-        let rx = udp_socket.try_clone().unwrap();
+        let rx = udp_socket.try_clone()?;
         let tx = udp_socket;
 
         let sending = self.sending.clone();
@@ -92,8 +92,7 @@ impl Server {
                             .expect("event consumer unavailable");
                     }
                 }
-            })
-            .unwrap();
+            })?;
 
         let sending = self.sending.clone();
 
@@ -124,8 +123,7 @@ impl Server {
                         }
                     }
                 }
-            })
-            .unwrap();
+            })?;
         Ok((receiver, sender))
     }
 
diff --git a/src/main.rs b/src/main.rs
index 04e8729..6e0a225 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,4 @@
-use std::sync::mpsc;
+use std::{sync::mpsc, process, env};
 
 use lan_mouse::{
     client::ClientManager,
@@ -6,12 +6,24 @@ use lan_mouse::{
     config, event, request,
 };
 
+fn usage() {
+    eprintln!("usage: {} [--backend <backend>] [--port <port>]",
+        env::args().next().unwrap_or("lan-mouse".into()));
+}
+
 pub fn main() {
     // parse config file
-    let config = config::Config::new("config.toml").unwrap();
+    let config = match config::Config::new() {
+        Err(e) => {
+            eprintln!("{e}");
+            usage();
+            process::exit(1);
+        }
+        Ok(config) => config,
+    };
 
     // port or default
-    let port = config.port.unwrap_or(42069);
+    let port = config.port;
 
     // event channel for producing events
     let (produce_tx, produce_rx) = mpsc::sync_channel(128);
@@ -20,26 +32,64 @@ pub fn main() {
     let (consume_tx, consume_rx) = mpsc::sync_channel(128);
 
     // create client manager
-    let mut client_manager = ClientManager::new(&config);
+    let mut client_manager = match ClientManager::new(&config) {
+        Err(e) => {
+            eprintln!("{e}");
+            process::exit(1);
+        }
+        Ok(m) => m,
+    };
 
     // start receiving client connection requests
     let (request_server, request_thread) = request::Server::listen(port).unwrap();
 
     // start producing and consuming events
-    let event_producer = producer::start(produce_tx, client_manager.get_clients(), request_server);
-    let event_consumer = consumer::start(consume_rx, client_manager.get_clients(), config.backend);
+    let event_producer = match producer::start(produce_tx, client_manager.get_clients(), request_server) {
+        Err(e) => {
+            eprintln!("Could not start event producer: {e}");
+            None
+        },
+        Ok(p) => Some(p),
+    };
+    let event_consumer = match consumer::start(consume_rx, client_manager.get_clients(), config.backend) {
+        Err(e) => {
+            eprintln!("Could not start event consumer: {e}");
+            None
+        },
+        Ok(p) => Some(p),
+    };
+
+    if event_consumer.is_none() && event_producer.is_none() {
+        process::exit(1);
+    }
 
     // start sending and receiving events
-    let event_server = event::server::Server::new(port);
-    let (receiver, sender) = event_server
-        .run(&mut client_manager, produce_rx, consume_tx)
-        .unwrap();
+    let event_server = match event::server::Server::new(port) {
+        Ok(s) => s,
+        Err(e) => {
+            eprintln!("{e}");
+            process::exit(1);
+        }
+    };
+    let (receiver, sender) = match event_server.run(&mut client_manager, produce_rx, consume_tx) {
+        Ok((r,s)) => (r,s),
+        Err(e) => {
+            eprintln!("{e}");
+            process::exit(1);
+        }
+    };
 
     request_thread.join().unwrap();
 
+    // stop receiving events and terminate event-consumer
     receiver.join().unwrap();
-    sender.join().unwrap();
+    if let Some(thread) = event_consumer {
+        thread.join().unwrap();
+    }
 
-    event_producer.join().unwrap();
-    event_consumer.join().unwrap();
+    // stop producing events and terminate event-sender
+    if let Some(thread) = event_producer {
+        thread.join().unwrap();
+    }
+    sender.join().unwrap();
 }
diff --git a/src/producer.rs b/src/producer.rs
index 3c3aadd..6824110 100644
--- a/src/producer.rs
+++ b/src/producer.rs
@@ -1,6 +1,6 @@
 #[cfg(unix)]
 use std::env;
-use std::{thread::{JoinHandle, self}, sync::mpsc::SyncSender};
+use std::{thread::{JoinHandle, self}, sync::mpsc::SyncSender, error::Error};
 
 use crate::{client::{Client, ClientHandle}, event::Event, request::Server};
 
@@ -16,8 +16,8 @@ pub fn start(
     produce_tx: SyncSender<(Event, ClientHandle)>,
     clients: Vec<Client>,
     request_server: Server,
-) -> JoinHandle<()> {
-    thread::Builder::new()
+) -> Result<JoinHandle<()>, Box<dyn Error>> {
+    Ok(thread::Builder::new()
         .name("event producer".into())
         .spawn(move || {
             #[cfg(windows)]
@@ -48,6 +48,5 @@ pub fn start(
                     producer::wayland::run(produce_tx, request_server, clients);
                 }
             }
-        })
-        .unwrap()
+        })?)
 }
diff --git a/src/request.rs b/src/request.rs
index 197f590..b4dd62f 100644
--- a/src/request.rs
+++ b/src/request.rs
@@ -60,11 +60,13 @@ impl Server {
 
     pub fn listen(port: u16) -> Result<(Server, JoinHandle<()>), Box<dyn Error>> {
         let data: Arc<RwLock<HashMap<Request, MmapMut>>> = Arc::new(RwLock::new(HashMap::new()));
-        let listen_addr = SocketAddr::new("0.0.0.0".parse().unwrap(), port);
+        let listen_addr = SocketAddr::new("0.0.0.0".parse()?, port);
         let server = Server { data };
         let server_copy = server.clone();
-        let thread = thread::spawn(move || {
-            let listen_socket = TcpListener::bind(listen_addr).unwrap();
+        let listen_socket = TcpListener::bind(listen_addr)?;
+        let thread = thread::Builder::new()
+            .name("tcp server".into())
+            .spawn(move || {
             for stream in listen_socket.incoming() {
                 match stream {
                     Ok(stream) => {
@@ -75,7 +77,7 @@ impl Server {
                     }
                 }
             }
-        });
+        })?;
         Ok((server_copy, thread))
     }