udp->source = 0x00000
时间: 2024-05-20 21:17:01 浏览: 8
This is not a complete statement as it is missing the rest of the code. However, based on what is written, it appears to be setting the source port of a UDP packet to 0x00000, which is equivalent to decimal 0. The source port is a 16-bit field in the UDP header that identifies the port number of the sending application. Setting it to 0 may cause issues as it is a well-known reserved port and may be used for specific purposes by the operating system or network protocols.
相关问题
udp校验和c语言代码
以下是一个简单的 UDP 校验和计算的 C 语言代码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
unsigned short checksum(unsigned short *buf, int nwords)
{
unsigned long sum;
for (sum = 0; nwords > 0; nwords--)
sum += *buf++;
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return (unsigned short)(~sum);
}
int main(int argc, char **argv)
{
char *data = "Hello, world!";
int datalen = strlen(data);
int total_len = sizeof(struct udphdr) + datalen;
unsigned char *packet = malloc(total_len);
struct udphdr *udp = (struct udphdr *)packet;
udp->source = htons(1234);
udp->dest = htons(5678);
udp->len = htons(total_len);
udp->check = 0;
memcpy(packet + sizeof(struct udphdr), data, datalen);
udp->check = checksum((unsigned short *)packet, total_len / 2);
printf("UDP checksum: 0x%04x\n", udp->check);
free(packet);
return 0;
}
```
这个代码演示了如何计算 UDP 数据包的校验和。它使用了一个简单的算法,将数据包中所有 16 位的字累加起来,然后将结果的高 16 位和低 16 位相加,再加上进位的 1,最后取反得到校验和。
tcp.port == 80 || udp.port == 80
引用提供了一些关于过滤端口的例子,其中tcp.port eq 80表示无论是源端口还是目标端口都显示为80的数据包,而tcp.dstport == 80表示只显示目标端口为80的tcp协议数据包,tcp.srcport == 80表示只显示来源端口为80的tcp协议数据包。提供了判断含有命令编码的MSN数据包的方法,其中tcp.port == 1863 || tcp.port == 80表示端口为1863或者80的数据包,tcp >= 41 && tcp <= 5A && tcp >= 41 && tcp <= 5A && tcp >= 41 && tcp <= 5A表示数据包前三个字节为大写字母,tcp == 20表示第四个字节为0x20,msn是属于TCP协议的。<em>1</em><em>2</em><em>3</em>
#### 引用[.reference_title]
- *1* *2* *3* [Wireshark 常用的抓包过滤表达式](https://blog.csdn.net/gybshen/article/details/104797739)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v92^chatsearchT0_1"}} ] [.reference_item]
[ .reference_list ]
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