.build(),
    )

    val call1 = client.newCall(Request(server.url("/")))
    call1.execute().use { response ->
      val source = response.body.source()
      assertThat(response.header("h1")).isEqualTo("v1")
      assertThat(source.readUtf8()).isEqualTo("Hello")
      assertThat(response.trailers()).isEqualTo(headersOf("t1", "v2"))
    }

    val call2 = client.newCall(Request(server.url("/")))

  fun increasingMaxRequestsPromotesJobsImmediately() {
    dispatcher.maxRequests = 2
    client.newCall(newRequest("http://a/1")).enqueue(callback)
    client.newCall(newRequest("http://b/1")).enqueue(callback)
    client.newCall(newRequest("http://c/1")).enqueue(callback)
    client.newCall(newRequest("http://a/2")).enqueue(callback)
    client.newCall(newRequest("http://b/2")).enqueue(callback)

    )
    server.enqueue(
      MockResponse(body = "GHI"),
    )
    val call1 = client.newCall(Request(server.url("/")))
    val response1 = call1.execute()
    val call2 = client.newCall(Request(server.url("/")))
    val response2 = call2.execute()
    val call3 = client.newCall(Request(server.url("/")))
    val response3 = call3.execute()
    assertThat(response1.body.string()).isEqualTo("ABC")

    val request = Request.Builder().url(server.url("/")).build()

    client.newCall(request).execute().use { response ->
      assertEquals(200, response.code)
    }

    client.connectionPool.evictAll()
    assertEquals(0, client.connectionPool.connectionCount())

    client.newCall(request).execute().use { response ->
      assertEquals(200, response.code)
    }

    server.protocols = listOf(Protocol.HTTP_2, Protocol.HTTP_1_1)
    server.enqueue(MockResponse())
    server.enqueue(MockResponse())

    client
      .newCall(Request(server.url("/")))
      .execute()
      .close()

    client
      .newCall(Request(server.url("/")))
      .execute()
      .close()

    assertThat(listener.recordedEventTypes()).containsExactly(
      "ConnectStart",

              val responseA = client.newCall(requestA).execute()
              assertThat(responseA.body.string()).isEqualTo("a")
            }
            chain.proceed(chain.request())
          },
        ).build()
    val requestB =
      Request
        .Builder()
        .url(server.url("/b"))
        .build()
    val responseB = client.newCall(requestB).execute()

    server.enqueue(MockResponse(body = "ghi"))
    client.newCall(Request.Builder().url(server.url("/a")).build()).enqueue(callback)
    callback.await(server.url("/a")).assertBody("abc")
    client.newCall(Request.Builder().url(server.url("/b")).build()).enqueue(callback)
    callback.await(server.url("/b")).assertBody("def")
    client.newCall(Request.Builder().url(server.url("/c")).build()).enqueue(callback)

  }

  @AfterEach
  fun tearDown() {
    executorService.shutdown()
  }

  @Test
  @Throws(IOException::class)
  fun http1DoesntSupportDuplex() {
    val call =
      client.newCall(
        Request
          .Builder()
          .url(server.url("/"))
          .post(AsyncRequestBody())
          .build(),
      )
    assertFailsWith<ProtocolException> {
      call.execute()

    ```kotlin
      private val client = OkHttpClient()

      fun run() {
        val request = Request.Builder()
            .url("https://publicobject.com/helloworld.txt")
            .build()

        client.newCall(request).execute().use { response ->
          if (!response.isSuccessful) throw IOException("Unexpected code $response")

          for ((name, value) in response.headers) {
            println("$name: $value")
          }

      )
    serverIpv4.enqueue(
      MockResponse(body = "unexpected call to IPv4"),
    )
    serverIpv6.enqueue(
      MockResponse(body = "hello from IPv6"),
    )

    val call = client.newCall(Request(url))
    val response = call.execute()
    assertThat(response.body.string()).isEqualTo("hello from IPv6")

    // In the process we made one successful connection attempt.