diff --git a/ktor-client/ktor-client-cio/jvm/test/io/ktor/client/engine/cio/CIORequestTest.kt b/ktor-client/ktor-client-cio/jvm/test/io/ktor/client/engine/cio/CIORequestTest.kt
index 6d1b962a79..0bdca5a931 100644
--- a/ktor-client/ktor-client-cio/jvm/test/io/ktor/client/engine/cio/CIORequestTest.kt
+++ b/ktor-client/ktor-client-cio/jvm/test/io/ktor/client/engine/cio/CIORequestTest.kt
@@ -5,6 +5,7 @@
 package io.ktor.client.engine.cio
 
 import io.ktor.client.call.*
+import io.ktor.client.network.sockets.*
 import io.ktor.client.plugins.*
 import io.ktor.client.request.*
 import io.ktor.client.statement.*
@@ -147,13 +148,19 @@ class CIORequestTest : TestWithKtor() {
         }
 
         test { client ->
+            var fail: Throwable? = null
             for (i in 0..1000) {
                 try {
                     client.get("http://something.wrong").body<String>()
-                } catch (cause: UnresolvedAddressException) {
-                    // ignore
+                } catch (cause: Throwable) {
+                    fail = cause
                 }
             }
+
+            assertNotNull(fail)
+            if (fail !is ConnectTimeoutException && fail !is UnresolvedAddressException) {
+                fail("Expected ConnectTimeoutException or UnresolvedAddressException, got $fail", fail)
+            }
         }
     }
 }
diff --git a/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/CIOEngine.kt b/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/CIOEngine.kt
index a2aa49ea07..0f4ba1c93d 100644
--- a/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/CIOEngine.kt
+++ b/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/CIOEngine.kt
@@ -33,7 +33,11 @@ internal class CIOEngine(
 
     private val selectorManager: SelectorManager by lazy { SelectorManager(dispatcher) }
 
-    private val connectionFactory = ConnectionFactory(selectorManager, config.maxConnectionsCount)
+    private val connectionFactory = ConnectionFactory(
+        selectorManager,
+        config.maxConnectionsCount,
+        config.endpoint.maxConnectionsPerRoute
+    )
 
     private val requestsJob: CoroutineContext
 
@@ -42,6 +46,7 @@ internal class CIOEngine(
     private val proxy: ProxyConfig? = when (val type = config.proxy?.type) {
         ProxyType.SOCKS,
         null -> null
+
         ProxyType.HTTP -> config.proxy
         else -> throw IllegalStateException("CIO engine does not currently support $type proxies.")
     }
diff --git a/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/ConnectionFactory.kt b/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/ConnectionFactory.kt
index 3b39274534..dd2c3139dc 100644
--- a/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/ConnectionFactory.kt
+++ b/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/ConnectionFactory.kt
@@ -6,29 +6,37 @@ package io.ktor.client.engine.cio
 
 import io.ktor.network.selector.*
 import io.ktor.network.sockets.*
+import io.ktor.util.collections.*
 import kotlinx.coroutines.sync.*
 
 internal class ConnectionFactory(
     private val selector: SelectorManager,
-    maxConnectionsCount: Int
+    connectionsLimit: Int,
+    private val addressConnectionsLimit: Int
 ) {
-    private val semaphore = Semaphore(maxConnectionsCount)
+    private val limit = Semaphore(connectionsLimit)
+    private val addressLimit = ConcurrentMap<InetSocketAddress, Semaphore>()
 
     suspend fun connect(
         address: InetSocketAddress,
         configuration: SocketOptions.TCPClientSocketOptions.() -> Unit = {}
     ): Socket {
-        semaphore.acquire()
+        limit.acquire()
+        val addressSemaphore = addressLimit.computeIfAbsent(address) { Semaphore(addressConnectionsLimit) }
+        addressSemaphore.acquire()
+
         return try {
             aSocket(selector).tcpNoDelay().tcp().connect(address, configuration)
         } catch (cause: Throwable) {
             // a failure or cancellation
-            semaphore.release()
+            addressSemaphore.release()
+            limit.release()
             throw cause
         }
     }
 
-    fun release() {
-        semaphore.release()
+    fun release(address: InetSocketAddress) {
+        addressLimit[address]!!.release()
+        limit.release()
     }
 }
diff --git a/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/Endpoint.kt b/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/Endpoint.kt
index c6e95c800f..22cbe2401e 100644
--- a/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/Endpoint.kt
+++ b/ktor-client/ktor-client-cio/jvmAndNix/src/io/ktor/client/engine/cio/Endpoint.kt
@@ -188,7 +188,7 @@ internal class Endpoint(
                     } catch (_: Throwable) {
                     }
 
-                    connectionFactory.release()
+                    connectionFactory.release(address)
                     throw cause
                 }
             }
@@ -229,7 +229,8 @@ internal class Endpoint(
     }
 
     private fun releaseConnection() {
-        connectionFactory.release()
+        val address = InetSocketAddress(host, port)
+        connectionFactory.release(address)
         connections.decrementAndGet()
     }
 
diff --git a/ktor-client/ktor-client-mock/common/src/io/ktor/client/engine/mock/MockUtils.kt b/ktor-client/ktor-client-mock/common/src/io/ktor/client/engine/mock/MockUtils.kt
index c96501da33..c7efda3aea 100644
--- a/ktor-client/ktor-client-mock/common/src/io/ktor/client/engine/mock/MockUtils.kt
+++ b/ktor-client/ktor-client-mock/common/src/io/ktor/client/engine/mock/MockUtils.kt
@@ -31,8 +31,8 @@ public suspend fun OutgoingContent.toByteArray(): ByteArray = when (this) {
     else -> ByteArray(0)
 }
 
-@OptIn(DelicateCoroutinesApi::class)
 @Suppress("KDocMissingDocumentation")
+@OptIn(DelicateCoroutinesApi::class)
 public suspend fun OutgoingContent.toByteReadPacket(): ByteReadPacket = when (this) {
     is OutgoingContent.ByteArrayContent -> ByteReadPacket(bytes())
     is OutgoingContent.ReadChannelContent -> readFrom().readRemaining()