ORA-29276: transfer timeout. Can someone help.

In 11203 database (R12.1.3 instance)

Declare

   req         Utl_Http.Req;

   o_resp      utl_http.Resp;

   v_url       Varchar2(250);

   v_line      Varchar2(4000);

begin

    v_url       := 'http://172.16.184.21/pstprnt';

    UTL_HTTP.set_transfer_timeout(180);

    req := Utl_Http.Begin_Request (url => v_url, method => 'POST', http_version => 'HTTP/1.1');

    utl_http.set_header(req, 'Transfer-Encoding', 'chunked');

    utl_http.set_header(req, 'Content-Type', 'text/plain');

    v_line:='<?xml version="1.0" standalone="no"?>';

    v_line:=v_line||'<!DOCTYPE labels SYSTEM "label.dtd">';

    v_line:=v_line||'<labels _FORMAT="E:NDFLBL13.ZPL" _QUANTITY="1" _PRINTERNAME="Printer 1" _JOBNAME="LBL101">';

    v_line:=v_line||'<label>';