diff --git a/tests/qemu-iotests/233 b/tests/qemu-iotests/233
index 057cad2044..a5c17c3963 100755
--- a/tests/qemu-iotests/233
+++ b/tests/qemu-iotests/233
@@ -49,7 +49,6 @@ _supported_proto file
 # If porting to non-Linux, consider using socat instead of ss in common.nbd
 _require_command QEMU_NBD
 
-nbd_server_set_tcp_port
 tls_x509_init
 
 echo
diff --git a/tests/qemu-iotests/common.nbd b/tests/qemu-iotests/common.nbd
index 25fc9ffaa4..24b01b60aa 100644
--- a/tests/qemu-iotests/common.nbd
+++ b/tests/qemu-iotests/common.nbd
@@ -22,6 +22,11 @@
 nbd_unix_socket="${TEST_DIR}/qemu-nbd.sock"
 nbd_tcp_addr="127.0.0.1"
 nbd_pid_file="${TEST_DIR}/qemu-nbd.pid"
+nbd_stderr_fifo="${TEST_DIR}/qemu-nbd.fifo"
+
+# If bash version is >= 4.1, this will be overwritten by a dynamically
+# assigned file descriptor value.
+nbd_fifo_fd=10
 
 nbd_server_stop()
 {
@@ -33,77 +38,62 @@ nbd_server_stop()
             kill "$NBD_PID"
         fi
     fi
-    rm -f "$nbd_unix_socket"
-}
-
-nbd_server_wait_for_unix_socket()
-{
-    pid=$1
-
-    for ((i = 0; i < 300; i++))
-    do
-        if [ -r "$nbd_unix_socket" ]; then
-            return
-        fi
-        kill -s 0 $pid 2>/dev/null
-        if test $? != 0
-        then
-            echo "qemu-nbd unexpectedly quit"
-            exit 1
-        fi
-        sleep 0.1
-    done
-    echo "Failed in check of unix socket created by qemu-nbd"
-    exit 1
+    rm -f "$nbd_unix_socket" "$nbd_stderr_fifo"
 }
 
 nbd_server_start_unix_socket()
 {
     nbd_server_stop
-    $QEMU_NBD -v -t -k "$nbd_unix_socket" "$@" &
-    nbd_server_wait_for_unix_socket $!
-}
-
-nbd_server_set_tcp_port()
-{
-    (ss --help) >/dev/null 2>&1 || _notrun "ss utility not found, skipping test"
-
-    for ((port = 10809; port <= 10909; port++))
-    do
-        if ! ss -tln | grep -sqE ":$port\b"; then
-            nbd_tcp_port=$port
-            return
-        fi
-    done
-
-    echo "Cannot find free TCP port for nbd in range 10809-10909"
-    exit 1
-}
-
-nbd_server_wait_for_tcp_socket()
-{
-    pid=$1
-
-    for ((i = 0; i < 300; i++))
-    do
-        if ss -tln | grep -sqE ":$nbd_tcp_port\b"; then
-            return
-        fi
-        kill -s 0 $pid 2>/dev/null
-        if test $? != 0
-        then
-            echo "qemu-nbd unexpectedly quit"
-            exit 1
-        fi
-        sleep 0.1
-    done
-    echo "Failed in check of TCP socket created by qemu-nbd"
-    exit 1
+    $QEMU_NBD -v -t -k "$nbd_unix_socket" --fork "$@"
 }
 
 nbd_server_start_tcp_socket()
 {
     nbd_server_stop
-    $QEMU_NBD -v -t -b $nbd_tcp_addr -p $nbd_tcp_port "$@" &
-    nbd_server_wait_for_tcp_socket $!
+
+    mkfifo "$nbd_stderr_fifo"
+    for ((port = 10809; port <= 10909; port++))
+    do
+        # Redirect stderr to FIFO, so we can later decide whether we
+        # want to read it or to redirect it to our stderr, depending
+        # on whether the command fails or not
+        $QEMU_NBD -v -t -b $nbd_tcp_addr -p $port --fork "$@" \
+            2> "$nbd_stderr_fifo" &
+
+        # Taken from common.qemu
+        if [[ "${BASH_VERSINFO[0]}" -ge "5" ||
+            ("${BASH_VERSINFO[0]}" -ge "4" && "${BASH_VERSINFO[1]}" -ge "1") ]]
+        then
+            exec {nbd_fifo_fd}<"$nbd_stderr_fifo"
+        else
+            let _nbd_fifo_fd++
+            eval "exec ${_nbd_fifo_fd}<'$nbd_stderr_fifo'"
+        fi
+        wait $!
+
+        if test $? == 0
+        then
+            # Success, redirect qemu-nbd's stderr to our stderr
+            nbd_tcp_port=$port
+            (cat <&$nbd_fifo_fd >&2) &
+            eval "exec $nbd_fifo_fd>&-"
+            return
+        fi
+
+        # Failure, read the output
+        output=$(cat <&$nbd_fifo_fd)
+        eval "exec $nbd_fifo_fd>&-"
+
+        if ! echo "$output" | grep -q "Address already in use"
+        then
+            # Unknown error, print it
+            echo "$output" >&2
+            rm -f "$nbd_stderr_fifo"
+            exit 1
+        fi
+    done
+
+    echo "Cannot find free TCP port for nbd in range 10809-10909"
+    rm -f "$nbd_stderr_fifo"
+    exit 1
 }