<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def sendhello(self):

 try:
 # send hello
 cli_hello_msg = "<hello>\n" +\
 " <capabilities>\n" +\
 " <capability>urn:ietf:params:netconf:base:1.0</capability>\n" +\
 " </capabilities>\n" +\
 "</hello>\n"
 self._cParams.set('cli_hello', cli_hello_msg)
 self._hConn.sendmsg(cli_hello_msg)
 
 # recv hello
 ser_hello_msg = self._hConn.recvmsg()
 self._cParams.set('ser_hello', ser_hello_msg)
 except:
 print 'BNClient: Call sendhello fail'
 sys.exit()
 
 """ end of function exchgcaps """