ozeki vs now
ozeki have more API support to java. both can send sms from java through http, but there is no java api in nowsms. ozeki has java api to send and receive sms through tcp.
http://www.ozekisms.com/index.php?owpn=584&infoe=java-sms-sdk-sms-over-tcp-ip
http://www.nowsms.com/discus/messages/1/24601.html

learn about jetty
http://wiki.eclipse.org/Jetty/Tutorial/Embedding_Jetty

The trial version of NowSMS has a 30 message per minute limitation.
http://www.nowsms.com/discus/messages/1/16578.html
Try enabling "SMS Access" = "GPRS" in the properties for the GSM modem in the "SMSC" list. 
P.S. - Keep in mind that you can also add additional modems to improve throughput.


SMSLib
1 sms per 3 seconds
19 sms / minute


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