udp.c

本代码是本人毕设所做的GPRS数传系统的软件部分

#include "ip.h"
#include "commdrv.h"

#include "udp.h"
#include "ppp.h"
#define UDP_HEADER_LENGTH 8
static WORD UDPLocalPort = 1080; // Default UDP port (can be set to anything)
static void UDPDefaultCallBack (BYTE *udpdata, BYTE size, DWORD RemoteIP, WORD Port);
static UDPCALLBACK UDPCallback = UDPDefaultCallBack;
extern UDPDatagram *udp_in; // Pointer to incoming UDP packet
extern UDPDatagram *udp_out; // Pointer for output UDP packet
/***********************************************************************
Function : UDPSetCallbackProc
Parameters : Proc: A pointer to a function to callback each time a UDP/IP
packet is received from the Internet
Date : December 2000
Desc : Sets the callback function to call each time a UDP packet is received
over the physical interface
***********************************************************************/
void UDPSetCALLBACK (UDPCALLBACK Proc) {
DisableInterrupts;
UDPCallback = Proc;
EnableInterrupts;
}
/***********************************************************************
Function : UDPDefaultCallBack
Parameters : None
Date : December 2000
Desc : The default callback available after RESET not accesible
from outside this module
***********************************************************************/
static void UDPDefaultCallBack (BYTE *udpdata, BYTE size, DWORD RemoteIP, WORD Port) {

}
/***********************************************************************
Function : UDPBind
Parameters : Port: local port to use in UDP packets to transmit
Date : November 2000
Desc : Specifies the local port to use for sending UDP
packets over IP
***********************************************************************/
void UDPBind (WORD Port) {
UDPLocalPort = Port; // Set source UDP port
}
/**********************************************************************
Function : UDP_Checksum
Parameters : udp: A pointer to the start of a udp/ip packet (0x45)
Date : November 2000
Desc : Calculates the pseudo-header checksum of a UDP packet
***********************************************************************/
WORD UDP_Checksum (BYTE* udp) {
DWORD Checksum = 0;
Checksum = IPCheckSum (&(udp[12]), (8 + (udp[25]) >> 1));
Checksum = ~Checksum + 0x11;
Checksum += udp [25];
Checksum = (Checksum >> 16) + (Checksum & 0xFFFF);
Checksum += (Checksum >> 16);
return (WORD)~Checksum;
}
/***********************************************************************
Function : UDPHandler
Parameters : udp: a pointer to the udp (struct UDPDatagram) packet received
Date : November 2000
Desc : Invokes the callback proc so the application can handle the
UDP data received
***********************************************************************/
void UDP_Handler (UDPDatagram *udp) {
udp_in =udp;
udp_in->Payload [udp_in->Length - UDP_HEADER_LENGTH] = 0x00;
UDPCallback ( // Invoque the CALLBACK function
(BYTE *)udp_in->Payload,
((udp_in->Length)- UDP_HEADER_LENGTH),
*((DWORD *)&udp_in->SourceIP),
udp_in->DestPort);
}
/***********************************************************************
Function : UDPSendData
Parameters : BYTE Ip[]: The IP address of the remote host
Port: UDP port of the remote host
Payload: Data to send
Size: Number of bytes to send to remote host
Date : November 2000
Desc : Sends data (payload) over UDP to a remote host specified by IP [] using
Port as the destination UDP port.
***********************************************************************/
void UDPSendData (BYTE Ip[], WORD Port, BYTE* Payload, BYTE size) {
WORD Checksum = 0;
ip_out->DestAddress [0] = Ip [0]; // Store source and destination
ip_out->DestAddress [1] = Ip [1]; // IP addresses
ip_out->DestAddress [2] = Ip [2];
ip_out->DestAddress [3] = Ip [3];
ip_out->SourceAddress [0] = IPAddress [0];
ip_out->SourceAddress [1] = IPAddress [1];
ip_out->SourceAddress [2] = IPAddress [2];
ip_out->SourceAddress [3] = IPAddress [3];
udp_out = (UDPDatagram *) &ip_out->SourceAddress;
// Insert Data Payload if available as an argument
if (Payload)
Move (Payload, &udp_out->Payload[0], size);
// Format payload as a null terminated string
udp_out->Payload[size] = 0x00;
if (size % 2) { // Pad the payload
size++;
}
udp_out->Length = size + UDP_HEADER_LENGTH; // Calculate the UDP length
ip_out->Length = size + UDP_HEADER_LENGTH + 20;// get IP packet length
ip_out->Protocol = UDP; // Protocol set to UDP
udp_out->SourcePort = htons(UDPLocalPort);// Set source and destination ports
udp_out->DestPort = htons(Port);
udp_out->LengthUpper = 0; // Packet cannot be longer than 256
// bytes
// (in this implementation)
udp_out->Checksum = 0; // Set checksum to 0
Checksum = UDP_Checksum ((BYTE *)ip_out); // Obtain the packet checksum
udp_out->Checksum = htons (Checksum);
IPNetSend (ip_out); // Send the packet to the IP layer
}