diff --git a/client/inc/nb65_constants.i b/client/inc/nb65_constants.i
index 9a66ffd..7d4f1ee 100644
--- a/client/inc/nb65_constants.i
+++ b/client/inc/nb65_constants.i
@@ -2,9 +2,17 @@
 
 NB65_API_VERSION=$0001
 
-NB65_DISPATCH_VECTOR = $800d 
-NB65_PERIODIC_PROCESSING_VECTOR =$8010
-NB65_VBL_VECTOR =$8013
+NB65_DISPATCH_VECTOR            = $800d 
+NB65_PERIODIC_PROCESSING_VECTOR = $8010
+NB65_VBL_VECTOR                 = $8013
+
+;offsets in IP packet of various interesting bits:
+NB65_IP_SRC	          = 12  ;offset of "source address" field in an IP packet header
+NB65_IP_DEST		      = 16  ;offset of "destination address" field in an IP packet header
+NB65_UDP_SRC_PORT	    = 20  ;offset of udp source port field in ip packet
+NB65_UDP_DEST_PORT    = 22  ;offset of udp source port field in ip packet
+NB65_UDP_DATA_LENGTH  = 24  ;offset of length field in udp packet
+NB65_UDP_DATA	        = 28  ;offset of data in udp packet
 
 ;offsets in NB65 configuration structure
 NB65_CFG_MAC        = $00     ;6 byte MAC address
@@ -46,7 +54,8 @@ NB65_TFTP_DOWNLOAD            =$06 ;inputs: AX points to a TFTP parameter struct
 NB65_DNS_RESOLVE_HOSTNAME     =$07 ;inputs: AX points to a DNS parameter structure, outputs: DNS param structure updated with 
                                    ;NB65_DNS_HOSTNAME_IP updated with IP address corresponding to hostname.
 NB65_UDP_ADD_LISTENER         =$08 ;inputs: AX points to a UDP listener parameter structure, outputs: none
-
+NB65_GET_INPUT_PACKET_PTR     =$09 ;inputs: none, outputs: AX contains address of start of IP packet
+NB65_UNHOOK_VBL_IRQ           =$0A ;inputs: none, outputs: none (removes call to NB65_VBL_VECTOR on IRQ chain)
 NB65_GET_LAST_ERROR           =$FF ;no inputs, outputs A = error code (from last function that set the global error value, not necessarily the
                                    ;last function that was called)
 
diff --git a/client/ip65/function_dispatcher.s b/client/ip65/function_dispatcher.s
index 3605eca..e8bb143 100644
--- a/client/ip65/function_dispatcher.s
+++ b/client/ip65/function_dispatcher.s
@@ -23,6 +23,9 @@
 .import dns_ip
 .import dns_resolve
 .import dns_set_hostname
+.import udp_callback
+.import udp_add_listener
+.import ip_inp
 .zeropage
 nb65_params:		.res 2
 
@@ -177,10 +180,19 @@ irq_handler_installed:
   lda (nb65_params),y
   tax
   dey
+  lda (nb65_params),y
+  
   jmp udp_add_listener
 :
 
 
+  cpy #NB65_GET_INPUT_PACKET_PTR
+  bne :+
+  ldax #ip_inp
+  clc
+  rts
+:  
+
   cpy #NB65_GET_LAST_ERROR
   bne :+
   lda ip65_error
@@ -188,6 +200,16 @@ irq_handler_installed:
   rts
 :  
 
+  cpy #NB65_UNHOOK_VBL_IRQ
+  bne :+
+  ldax  jmp_old_irq+1
+  sei ;don't want any interrupts while we fiddle with the vector
+  stax  $314    ;previous IRQ handler
+  cli
+  clc
+  rts
+:  
+
 ;default function handler
   lda #NB65_ERROR_FUNCTION_NOT_SUPPORTED
   sta ip65_error