Hi,

      I performed the following:

      # kamcmd dbg.trace on
# curl --header 'Content-Type: application/json' \

--data-binary '{\

"jsonrpc": "2.0", \

"method": "ul.lookup", \

"params": [ "location",
"user@example.com"

      ], \

"id": 3 }' 
http://registrar.example.com/rpc

      # kamcmd dbg.trace off

      And the following was presented in the log file

      [5843]: ERROR: *** cfgtrace:request_route=[xhttp:request]
      c=[/etc/kamailio/routing_logic.cfg] l=301 a=63 n=assign

      [5843]: ERROR: *** cfgtrace:request_route=[xhttp:request]
      c=[/etc/kamailio/routing_logic.cfg] l=305 a=16 n=if

      [5843]: ERROR: *** cfgtrace:request_route=[xhttp:request]
      c=[/etc/kamailio/routing_logic.cfg] l=303 a=24 n=jsonrpc_dispatch

      [5843]: ERROR: *** cfgtrace:request_route=[xhttp:request]
      c=[/etc/kamailio/routing_logic.cfg] l=305 a=63 n=assign

      [5843]: ERROR: *** cfgtrace:request_route=[xhttp:request]
      c=[/etc/kamailio/routing_logic.cfg] l=313 a=16 n=if

      [5843]: ERROR: *** cfgtrace:request_route=[xhttp:request]
      c=[/etc/kamailio/routing_logic.cfg] l=314 a=28 n=xhttp_reply

      [5843]: ERROR: <core> [core/data_lump_rpl.c:83]:
      add_lump_rpl2(): LUMP_RPL_BODY already added!

      [5843]: ERROR: xhttp [xhttp_mod.c:410]: xhttp_send_reply(): Error
      while adding reply lump

      The relevent request route is as follows:

      # Handling HTTP events

      event_route[xhttp:request] {

              $var(xhttp_rpc_root) = $(hu{s.substr,0,4});

              if ($var(xhttp_rpc_root) == "/rpc") {

                      jsonrpc_dispatch();

              }

              $var(xhttp_rpc_root) = $(hu{s.substr,0,9});

              if ($var(xhttp_rpc_root) == "/http_rpc") {

                      dispatch_xhttp_rpc();

              }

              #$var(xhttp_rpc_root) = $(hu{s.substr,0,8});

              #if ($var(xhttp_rpc_root) == "/http_pi") {

              #        dispatch_xhttp_pi();

              #}

              xhttp_reply("200", "OK", "text/html",

                      "<html><body>Wrong URL
      $hu</body></html>");

      }

      Just looking at the above event route, do I need to "exit" the if
      statements above, would the last xhttp_reply be causing this
      error?

      Thanks

this sounds like the body for reply was already set. Can you enable
cfgtrace in debugger module and see what actions are executed in that
situation?