[tcp] tcpclient can't connect to tcpserver if server start later than client

[qiaojingx]

Description

tcpclient can't connect to tcpserver if server start later than client over 10s.

Test Code

TCPClient6.js;

tcpserver.py

# /usr/bin/python
# -*- coding: utf-8 -*-
import socket
import time
sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
server_address = ('2001:db8::2', 4242)
print "Starting up on %s:%s" % server_address
sock.bind(server_address)
sock.listen(1)
print "Waiting for a connection"
connection, client_address = sock.accept()
print "Connection from", client_address
while True:
        data = connection.recv(1024)
        print "Receive '%s'" % data
        connection.send(data)
        time.sleep(3)

Steps to Reproduction

1. Change host address in line 52 and 59 to 2001:db8::2 and change err.name in line 48 to err.name == "Error" in TCPClient6.js because of #1454 ;
2. Build TCPClient6.js on Arduino101.
3. Connect PC via BLE and add a new route for the bt0 interface: ip -6 route add 2001:db8::/64 dev bt0 ip -6 addr add 2001:db8::2 dev bt0
4. After 10s, start tcpserver by python tcpserver.py

Actual Result

tcpclient can't connect to tcpserver

Expected Result

tcpclient could connect to tcpserver whenever server started.

Test Builds

Branch	Commit Id	Target Device	Test Date	Result
master	e3e4dde	Arduino 101	Aug 11, 2017	Fail

Additional Information

[grgustaf]

I haven't looked at this yet, but clients expects servers to exist already. So this sounds like reasonable behavior, but we could also change the client to retry forever if we want. I assume it's just trying a certain number of times and then giving up.

[qiaojingx]

Verified with commit 0c0af9b in master. This issue is not reproduced on Arduino101 over Ethernet, FRDM-K64F and Qemu. But on Arduino101 over ble, this issue cannot be verified because of issue #1518.