diff --git a/protocol/src/master.rs b/protocol/src/master.rs
index 9272f7e..bba4a65 100644
--- a/protocol/src/master.rs
+++ b/protocol/src/master.rs
@@ -76,6 +76,10 @@ impl<'a> QueryServersResponse<&'a [u8]> {
             SocketAddrV4::new(ip, port)
         })
     }
+
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
 }
 
 impl<I> QueryServersResponse<I>
diff --git a/query/src/main.rs b/query/src/main.rs
index 64d597a..f986f30 100644
--- a/query/src/main.rs
+++ b/query/src/main.rs
@@ -7,10 +7,9 @@ use std::cmp;
 use std::collections::{HashMap, HashSet};
 use std::fmt;
 use std::io;
-use std::net::{Ipv4Addr, SocketAddrV4, UdpSocket};
+use std::net::{Ipv4Addr, SocketAddr, SocketAddrV4, UdpSocket};
 use std::process;
-use std::sync::{mpsc, Arc};
-use std::thread;
+use std::sync::Arc;
 use std::time::{Duration, Instant};
 
 use serde::{Serialize, Serializer};
@@ -50,34 +49,34 @@ enum ServerResultKind {
 
 #[derive(Clone, Debug, Serialize)]
 struct ServerResult {
-    address: String,
+    address: SocketAddrV4,
     ping: f32,
     #[serde(flatten)]
     kind: ServerResultKind,
 }
 
 impl ServerResult {
-    fn new(address: String, ping: f32, kind: ServerResultKind) -> Self {
+    fn new(address: SocketAddrV4, ping: f32, kind: ServerResultKind) -> Self {
         Self {
-            address: address.to_string(),
+            address,
             ping,
             kind,
         }
     }
 
-    fn ok(address: String, ping: f32, info: ServerInfo) -> Self {
+    fn ok(address: SocketAddrV4, ping: f32, info: ServerInfo) -> Self {
         Self::new(address, ping, ServerResultKind::Ok { info })
     }
 
-    fn timeout(address: String) -> Self {
+    fn timeout(address: SocketAddrV4) -> Self {
         Self::new(address, 0.0, ServerResultKind::Timeout)
     }
 
-    fn protocol(address: String, ping: f32) -> Self {
+    fn protocol(address: SocketAddrV4, ping: f32) -> Self {
         Self::new(address, ping, ServerResultKind::Protocol)
     }
 
-    fn error<T>(address: String, message: T) -> Self
+    fn error<T>(address: SocketAddrV4, message: T) -> Self
     where
         T: fmt::Display,
     {
@@ -90,7 +89,7 @@ impl ServerResult {
         )
     }
 
-    fn invalid<T>(address: String, ping: f32, message: T, response: &[u8]) -> Self
+    fn invalid<T>(address: SocketAddrV4, ping: f32, message: T, response: &[u8]) -> Self
     where
         T: fmt::Display,
     {
@@ -152,7 +151,7 @@ struct ListResult<'a> {
     master_timeout: u32,
     masters: &'a [Box<str>],
     filter: &'a str,
-    servers: &'a [&'a str],
+    servers: &'a [SocketAddrV4],
 }
 
 fn serialize_colored<S>(s: &str, ser: S) -> Result<S::Ok, S::Error>
@@ -203,159 +202,243 @@ impl fmt::Display for Colored<'_> {
     }
 }
 
-enum Message {
-    Servers(Vec<String>),
-    ServerResult(ServerResult),
-    End,
+fn get_socket_addrs<'a>(iter: impl Iterator<Item = &'a str>) -> Result<Vec<SocketAddrV4>, Error> {
+    use std::net::ToSocketAddrs;
+
+    let mut out = Vec::with_capacity(iter.size_hint().0);
+    for i in iter {
+        match i
+            .to_socket_addrs()?
+            .find(|i| matches!(i, SocketAddr::V4(_)))
+        {
+            Some(SocketAddr::V4(addr)) => out.push(addr),
+            _ => eprintln!("warn: failed to resolve address for {}", i),
+        }
+    }
+
+    Ok(out)
+}
+
+struct ServerQuery {
+    start: Instant,
+    protocol: usize,
 }
 
-fn cmp_address(a: &str, b: &str) -> cmp::Ordering {
-    match (a.parse::<SocketAddrV4>(), b.parse::<SocketAddrV4>()) {
-        (Ok(a), Ok(b)) => a.cmp(&b),
-        _ => a.cmp(b),
+impl ServerQuery {
+    fn ping(&self) -> f32 {
+        self.start.elapsed().as_micros() as f32 / 1000.0
     }
 }
 
-fn query_servers(
-    host: &str,
-    cli: &Cli,
-    timeout: Duration,
-    tx: &mpsc::Sender<Message>,
-) -> Result<(), Error> {
-    let sock = UdpSocket::bind("0.0.0.0:0")?;
-    sock.connect(host)?;
-
-    let mut buf = [0; 512];
-    let p = game::QueryServers {
-        region: server::Region::RestOfTheWorld,
-        last: SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), 0),
-        filter: cli.filter.as_str(),
-    };
-    let n = p.encode(&mut buf)?;
-    sock.send(&buf[..n])?;
-
-    let start_time = Instant::now();
-    while let Some(timeout) = timeout.checked_sub(start_time.elapsed()) {
-        sock.set_read_timeout(Some(timeout))?;
-        let n = match sock.recv(&mut buf) {
-            Ok(n) => n,
-            Err(e) => match e.kind() {
-                io::ErrorKind::AddrInUse | io::ErrorKind::WouldBlock => break,
-                _ => Err(e)?,
-            },
-        };
-        if let Ok(packet) = master::QueryServersResponse::decode(&buf[..n]) {
-            tx.send(Message::Servers(
-                packet.iter().map(|i| i.to_string()).collect(),
-            ))
-            .unwrap();
-        } else {
-            eprintln!("Unexpected packet from master {}", host);
+impl ServerQuery {
+    fn new(protocol: usize) -> Self {
+        Self {
+            start: Instant::now(),
+            protocol,
         }
     }
+}
 
-    Ok(())
+struct Scan<'a> {
+    cli: &'a Cli,
+    masters: Vec<SocketAddrV4>,
+    sock: UdpSocket,
 }
 
-fn get_server_info(
-    addr: String,
-    versions: &[u8],
-    timeout: Duration,
-) -> Result<ServerResult, Error> {
-    let sock = UdpSocket::bind("0.0.0.0:0")?;
-    sock.connect(&addr)?;
-    sock.set_read_timeout(Some(timeout))?;
-
-    let mut ping = 0.0;
-    for &i in versions {
-        let p = game::GetServerInfo::new(i);
-        let mut buf = [0; 2048];
-        let n = p.encode(&mut buf)?;
-        let start = Instant::now();
-        sock.send(&buf[..n])?;
-
-        let n = match sock.recv(&mut buf) {
-            Ok(n) => n,
-            Err(e) => match e.kind() {
-                io::ErrorKind::AddrInUse | io::ErrorKind::WouldBlock => {
-                    return Ok(ServerResult::timeout(addr));
-                }
-                _ => Err(e)?,
-            },
+impl<'a> Scan<'a> {
+    fn new(cli: &'a Cli) -> Result<Self, Error> {
+        Ok(Self {
+            cli,
+            masters: get_socket_addrs(cli.masters.iter().map(|i| i.as_ref()))?,
+            sock: UdpSocket::bind(SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), 0))?,
+        })
+    }
+
+    fn is_master(&self, addr: &SocketAddrV4) -> bool {
+        self.masters.iter().any(|i| i == addr)
+    }
+
+    fn query_servers(&self) -> Result<(), Error> {
+        let mut buf = [0; 512];
+        let packet = game::QueryServers {
+            region: server::Region::RestOfTheWorld,
+            last: SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), 0),
+            filter: self.cli.filter.as_str(),
         };
-        ping = start.elapsed().as_micros() as f32 / 1000.0;
+        let n = packet.encode(&mut buf)?;
+        let packet = &buf[..n];
 
-        let response = &buf[..n];
-        match server::GetServerInfoResponse::decode(response) {
-            Ok(packet) => {
-                let info = ServerInfo::from(packet);
-                return Ok(ServerResult::ok(addr, ping, info));
-            }
-            Err(ProtocolError::InvalidProtocolVersion) => {
-                // try another protocol version
-            }
-            Err(e) => {
-                return Ok(ServerResult::invalid(addr, ping, e, response));
-            }
+        for i in &self.masters {
+            self.sock.send_to(packet, i)?;
         }
+
+        Ok(())
     }
 
-    Ok(ServerResult::protocol(addr, ping))
-}
+    fn servers(&self) -> Result<HashSet<SocketAddrV4>, Error> {
+        self.query_servers()?;
 
-fn query_server_info(cli: &Arc<Cli>, servers: &[String]) -> Result<(), Error> {
-    let (tx, rx) = mpsc::channel();
-    let mut workers = 0;
-
-    if servers.is_empty() {
-        for i in cli.masters.iter() {
-            let master = i.to_owned();
-            let tx = tx.clone();
-            let timeout = Duration::from_secs(cli.master_timeout as u64);
-            let cli = cli.clone();
-            thread::spawn(move || {
-                if let Err(e) = query_servers(&master, &cli, timeout, &tx) {
-                    eprintln!("master({}) error: {}", master, e);
+        let mut set = HashSet::with_capacity(256);
+        let mut buf = [0; 2048];
+        let timeout = Duration::from_secs(self.cli.master_timeout as u64);
+        let start_time = Instant::now();
+
+        while let Some(timeout) = timeout.checked_sub(start_time.elapsed()) {
+            self.sock.set_read_timeout(Some(timeout))?;
+
+            let (n, from) = match self.sock.recv_from(&mut buf) {
+                Ok(x) => x,
+                Err(e) => match e.kind() {
+                    io::ErrorKind::AddrInUse => break,
+                    io::ErrorKind::WouldBlock => break,
+                    _ => Err(e)?,
+                },
+            };
+
+            let from = match from {
+                SocketAddr::V4(x) => x,
+                _ => todo!(),
+            };
+
+            if self.is_master(&from) {
+                if let Ok(packet) = master::QueryServersResponse::decode(&buf[..n]) {
+                    set.extend(packet.iter());
+                } else {
+                    eprintln!("warn: invalid packet from master {}", from);
                 }
-                tx.send(Message::End).unwrap();
-            });
-            workers += 1;
+            }
         }
-    } else {
-        tx.send(Message::Servers(servers.to_vec())).unwrap();
+
+        Ok(set)
     }
 
-    let mut servers = HashMap::new();
-    while let Ok(msg) = rx.recv() {
-        match msg {
-            Message::Servers(list) => {
-                for address in list {
-                    let tx = tx.clone();
-                    let timeout = Duration::from_secs(cli.server_timeout as u64);
-                    let versions = cli.protocol.clone();
-                    thread::spawn(move || {
-                        let result = get_server_info(address.clone(), &versions, timeout)
-                            .unwrap_or_else(|e| ServerResult::error(address, e));
-                        tx.send(Message::ServerResult(result)).unwrap();
-                        tx.send(Message::End).unwrap();
-                    });
-                    workers += 1;
+    fn server_info(
+        &self,
+        list: &[SocketAddrV4],
+    ) -> Result<HashMap<SocketAddrV4, ServerResult>, Error> {
+        let mut set = HashSet::new();
+        let mut active = HashMap::new();
+        let mut out = HashMap::new();
+        let mut buf = [0; 2048];
+
+        let now = Instant::now();
+        let master_timeout = Duration::from_secs(self.cli.master_timeout as u64);
+        let server_timeout = Duration::from_secs(self.cli.server_timeout as u64);
+        let master_end = now + master_timeout;
+        let mut server_end = now + server_timeout;
+
+        if list.is_empty() {
+            self.query_servers()?;
+        } else {
+            let mut buf = [0; 512];
+            let n = game::GetServerInfo::new(self.cli.protocol[0]).encode(&mut buf)?;
+
+            for addr in list.iter().filter(|i| set.insert(**i)) {
+                match self.sock.send_to(&buf[..n], addr) {
+                    Ok(_) => {
+                        let query = ServerQuery::new(0);
+                        server_end = query.start + server_timeout;
+                        active.insert(*addr, query);
+                    }
+                    Err(e) => {
+                        let res = ServerResult::error(*addr, e);
+                        out.insert(*addr, res);
+                    }
                 }
             }
-            Message::End => {
-                workers -= 1;
-                if workers == 0 {
-                    break;
-                }
+        }
+
+        loop {
+            let time = cmp::max(master_end, server_end);
+            match time.checked_duration_since(Instant::now()) {
+                Some(t) => self.sock.set_read_timeout(Some(t))?,
+                None => break,
             }
-            Message::ServerResult(result) => {
-                servers.insert(result.address.clone(), result);
+
+            let (n, from) = match self.sock.recv_from(&mut buf) {
+                Ok(x) => x,
+                Err(e) => match e.kind() {
+                    io::ErrorKind::AddrInUse => break,
+                    io::ErrorKind::WouldBlock => break,
+                    _ => Err(e)?,
+                },
+            };
+            let from = match from {
+                SocketAddr::V4(x) => x,
+                _ => todo!(),
+            };
+            let raw = &buf[..n];
+
+            if self.is_master(&from) {
+                if let Ok(packet) = master::QueryServersResponse::decode(raw) {
+                    for addr in packet.iter().filter(|i| set.insert(*i)) {
+                        let mut buf = [0; 512];
+                        let n = game::GetServerInfo::new(self.cli.protocol[0]).encode(&mut buf)?;
+
+                        match self.sock.send_to(&buf[..n], addr) {
+                            Ok(_) => {
+                                let query = ServerQuery::new(0);
+                                server_end = query.start + server_timeout;
+                                active.insert(addr, query);
+                            }
+                            Err(e) => {
+                                let res = ServerResult::error(addr, e);
+                                out.insert(addr, res);
+                            }
+                        }
+                    }
+                }
+            } else if let Some(query) = active.remove(&from) {
+                match server::GetServerInfoResponse::decode(raw) {
+                    Ok(packet) => {
+                        let info = ServerInfo::from(packet);
+                        let res = ServerResult::ok(from, query.ping(), info);
+                        out.insert(from, res);
+                    }
+                    Err(ProtocolError::InvalidProtocolVersion) => {
+                        let next_protocol = query.protocol + 1;
+                        if let Some(protocol) = self.cli.protocol.get(next_protocol) {
+                            let mut buf = [0; 512];
+                            let n = game::GetServerInfo::new(*protocol).encode(&mut buf)?;
+
+                            match self.sock.send_to(&buf[..n], from) {
+                                Ok(_) => {
+                                    active.insert(from, ServerQuery::new(next_protocol));
+                                }
+                                Err(e) => {
+                                    let res = ServerResult::error(from, e);
+                                    out.insert(from, res);
+                                }
+                            }
+                        } else {
+                            let res = ServerResult::protocol(from, query.ping());
+                            out.insert(from, res);
+                        }
+                    }
+                    Err(e) => {
+                        let res = ServerResult::invalid(from, query.ping(), e, raw);
+                        out.insert(from, res);
+                    }
+                }
             }
         }
+
+        for (addr, _) in active {
+            let res = ServerResult::timeout(addr);
+            out.insert(addr, res);
+        }
+
+        Ok(out)
     }
+}
+
+fn query_server_info(cli: &Arc<Cli>, servers: &[String]) -> Result<(), Error> {
+    let scan = Scan::new(cli)?;
+    let servers = get_socket_addrs(servers.iter().map(|i| i.as_str()))?;
+    let servers = scan.server_info(&servers)?;
 
     let mut servers: Vec<_> = servers.values().collect();
-    servers.sort_by(|a, b| cmp_address(&a.address, &b.address));
+    servers.sort_by(|a, b| a.address.cmp(&b.address));
 
     if cli.json || cli.debug {
         let result = InfoResult {
@@ -432,41 +515,9 @@ fn query_server_info(cli: &Arc<Cli>, servers: &[String]) -> Result<(), Error> {
 }
 
 fn list_servers(cli: &Arc<Cli>) -> Result<(), Error> {
-    let (tx, rx) = mpsc::channel();
-    let mut workers = 0;
-
-    for i in cli.masters.iter() {
-        let master = i.to_owned();
-        let tx = tx.clone();
-        let timeout = Duration::from_secs(cli.master_timeout as u64);
-        let cli = cli.clone();
-        thread::spawn(move || {
-            if let Err(e) = query_servers(&master, &cli, timeout, &tx) {
-                eprintln!("master({}) error: {}", master, e);
-            }
-            tx.send(Message::End).unwrap();
-        });
-        workers += 1;
-    }
-
-    let mut servers = HashSet::new();
-    while let Ok(msg) = rx.recv() {
-        match msg {
-            Message::Servers(list) => {
-                servers.extend(list);
-            }
-            Message::End => {
-                workers -= 1;
-                if workers == 0 {
-                    break;
-                }
-            }
-            _ => panic!(),
-        }
-    }
-
-    let mut servers: Vec<_> = servers.iter().map(|i| i.as_str()).collect();
-    servers.sort_by(|a, b| cmp_address(a, b));
+    let scan = Scan::new(cli)?;
+    let mut servers: Vec<_> = scan.servers()?.into_iter().collect();
+    servers.sort();
 
     if cli.json || cli.debug {
         let result = ListResult {