Hi, 
   I solved this.  The issue was on the client side.  I needed to confirm acceptance of the message on the client side and respond to FreeSWITCH:

http://www.sipml5.org/docgen/index.html#acceptMessageFunc

  After doing that FreeSWITCH no longer hangs, and confirms that the messages was sent successfully in the log.



On Fri, Jan 9, 2015 at 11:52 AM, Question Answer <questions.looking.for.answers@gmail.com> wrote:
Hi,
  I have successfully configured a SIPml5 client in Chrome to communicate with a local FreeSWITCH server.
  It is possible to successfully make calls, and use most applications in the freeswitch dial plan.
  
  Problem: I cannot figure out how to successfully send a custom SIP message from FreeSWITCH [via either the CLI or the dialplan] to the web client.
  The client actually *receives* the message, but FreeSWITCH then hangs for about 10s, times out and reports: 'Error! Message Not Sent Sent'.

  I run the following command from the CLI:

freeswitch> chat sip|1001@192.168.59.103|1000@172.17.0.19|test test test
send 764 bytes to ws/[192.168.59.3]:51933 at 09:48:10.190253:
   ------------------------------------------------------------------------
   MESSAGE sip:1000@192.168.59.3:51933 SIP/2.0
   Via: SIP/2.0/WS 172.17.0.19:5066;branch=z9hG4bKFpeyg98ZZ240r
   Route: <sip:1000@192.168.59.3:51933>;rtcweb-breaker=yes;transport=ws
   Max-Forwards: 70
   From: "1001" <sip:1001@192.168.59.103>;tag=U9prcNXypBBUr
   To: <sip:1000@192.168.59.3:51933>;rtcweb-breaker=yes;transport=ws
   Call-ID: 5b3c7d7c-8149-422c-9f0f-f1b3dd3661f2
   CSeq: 70061165 MESSAGE
   Contact: <sip:172.17.0.19>
   User-Agent: FreeSWITCH-mod_sofia/1.5.15b+git~20150106T091916Z~f48ec61d54~64bit
   Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE
   Supported: timer, path, replaces
   Content-Type: text/html
   Content-Length: 14
   X-FS-Sending-Message: 4a972b6a-3c72-4ba1-b7a4-de2d07760380

   test test test
   ------------------------------------------------------------------------
[~10 seconds pass...]
Error! Message Not Sent
...
freeswitch>

--------------------------------------------------------------------------------
But on the client side, in the Chrome developer console, I can see the following log messages:

SIPml-api.js?svn=222:1 __tsip_transport_ws_onmessage
2015-01-09 11:37:09.647SIPml-api.js?svn=222:1 recv=MESSAGE sip:1000@192.168.59.3:52190 SIP/2.0
Via: SIP/2.0/WS 172.17.0.19:5066;branch=z9hG4bKKtK1QNcem6XBQ
From: "1001"<sip:1001@192.168.59.103>;tag=29gZHme856Fmc
To: <sip:1000@192.168.59.3:52190>;rtcweb-breaker=yes;transport=ws
Contact: <sip:172.17.0.19>
Call-ID: 210f6e1f-0415-450b-bbb3-7725a6a37434
CSeq: 70061168 MESSAGE
Content-Type: text/html
Content-Length: 14
Max-Forwards: 70
User-Agent: FreeSWITCH-mod_sofia/1.5.15b+git~20150106T091916Z~f48ec61d54~64bit
Allow: INVITE,ACK,BYE,CANCEL,OPTIONS,MESSAGE,INFO,UPDATE,REGISTER,REFER,NOTIFY,PUBLISH,SUBSCRIBE
Supported: timer,path,replaces
X-FS-Sending-Message: 4a972b6a-3c72-4ba1-b7a4-de2d07760380

test test test
2015-01-09 11:37:09.647SIPml-api.js?svn=222:1 State machine: tsip_dialog_generic_Started_2_Incoming_X_iMessage
2015-01-09 11:37:09.649SIPml-api.js?svn=222:1 ==stack event = i_new_message XXX test test test
2015-01-09 11:37:09.649call.htm:964 test test test
----------------------------------------------------------------------------------

That is, the message is correctly received by the client, but FreeSWITCH doesn't seem to 'realise' this.
Perhaps I need to be sending some kind explicit confirmation back from the simpml5 client application?

Or perhaps there is some kind of mismatch with the SIP profile?  I have set the freeswitch log level to Debug, but the above is the only message I see, which is not particularly helpful.

Any insights would be appreciated!