diff --git a/hack/exec-tool b/hack/exec-tool
index 47b84ca..28a0882 100755
--- a/hack/exec-tool
+++ b/hack/exec-tool
@@ -24,7 +24,7 @@ ping)
     ;;
 iperf3)
     port=5001
-    with_set_x exec iperf3 --client "$ip" --port=$port --connect-timeout=$connect_timeout_sec "$@"
+    with_set_x exec iperf3 --client "$ip" --port=$port --connect-timeout=$((connect_timeout_sec * 1000)) "$@"
     ;;
 curl)
     port=8080
@@ -32,6 +32,6 @@ curl)
     ;;
 ab)
     port=8080
-    with_set_x exec ab -n 100 -c 20 -s $connect_timeout_sec "$@" "http://$ip:$port/" 
+    with_set_x exec ab -n 100 -c 20 -s $connect_timeout_sec "$@" "http://$ip:$port/"
     ;;
 esac
diff --git a/hack/run-checks b/hack/run-checks
new file mode 100755
index 0000000..72bead2
--- /dev/null
+++ b/hack/run-checks
@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+set -e
+cd "$(dirname "$0")/.."
+
+export PYTHONPATH=.
+
+set -x
+python -m pytest .
+python -m flake8 .  
\ No newline at end of file
diff --git a/sshuttle/firewall.py b/sshuttle/firewall.py
index 3e3bb64..9532ab0 100644
--- a/sshuttle/firewall.py
+++ b/sshuttle/firewall.py
@@ -224,7 +224,6 @@ def main(method_name, syslog):
     stdout.write(('READY %s\n' % method.name).encode('ASCII'))
     stdout.flush()
 
-
     def _read_next_string_line():
         try:
             line = stdin.readline(128)
diff --git a/sshuttle/ssnet.py b/sshuttle/ssnet.py
index 798e42a..6110b4c 100644
--- a/sshuttle/ssnet.py
+++ b/sshuttle/ssnet.py
@@ -432,7 +432,8 @@ class Mux(Handler):
     def flush(self):
         set_non_blocking_io(self.wfile.fileno())
         if self.outbuf and self.outbuf[0]:
-            wrote = _nb_clean(os.write, self.wfile.fileno(), self.outbuf[0])
+            wrote = _nb_clean(self.wfile.write, self.outbuf[0])
+            self.wfile.flush()
             debug2('mux wrote: %r/%d' % (wrote, len(self.outbuf[0])))
             if wrote:
                 self.outbuf[0] = self.outbuf[0][wrote:]
diff --git a/tests/client/test_firewall.py b/tests/client/test_firewall.py
index 02a73f7..f9d4fdb 100644
--- a/tests/client/test_firewall.py
+++ b/tests/client/test_firewall.py
@@ -21,7 +21,7 @@ NSLIST
 PORTS 1024,1025,1026,1027
 GO 1 - - 0x01 12345
 HOST 1.2.3.3,existing
-""".format(inet=AF_INET, inet6=AF_INET6))
+""".format(inet=AF_INET, inet6=AF_INET6).encode('ASCII'))
     stdout = Mock()
     return stdin, stdout