如果我在Wireshark中没有看到我的包裹，是否寄出了？

Question

我的任务是创建一个利用原始套接字的简单TCP扫描程序。我找到了一个包含所需代码的网页。编写和运行代码没问题，一切似乎都正常。但是，当我尝试在Wireshark中跟踪程序包时，它不存在。我浏览所有接口，我看任何接口，甚至尝试过滤结果，但无济于事。我的目标是从端口20的非循环接口（147.229.206.115）发送到www.google.com（172.217.23.196）以确定是否打开，关闭或过滤了一个程序包。该代码包含ip和tcp的自定义标头，因为我们必须手动设置：

struct ipheader {
    unsigned char      iph_ihl:5, /* Little-endian */
                        iph_ver:4;
    unsigned char      iph_tos;
    unsigned short int iph_len;
    unsigned short int iph_ident;
    unsigned char      iph_flags;
    unsigned short int iph_offset;
    unsigned char      iph_ttl;
    unsigned char      iph_protocol;
    unsigned short int iph_chksum;
    unsigned int       iph_sourceip;
    unsigned int       iph_destip;
};

struct tcpheader {
unsigned short int   tcph_srcport;
unsigned short int   tcph_destport;
unsigned int             tcph_seqnum;
unsigned int             tcph_acknum;
unsigned char          tcph_reserved:4, tcph_offset:4;
unsigned int
   tcp_res1:4,      /*little-endian*/
   tcph_hlen:4,     /*length of tcp header in 32-bit words*/
   tcph_fin:1,      /*Finish flag "fin"*/
   tcph_syn:1,       /*Synchronize sequence numbers to start a connection*/
   tcph_rst:1,      /*Reset flag */
   tcph_psh:1,      /*Push, sends data to the application*/
   tcph_ack:1,      /*acknowledge*/
   tcph_urg:1,      /*urgent pointer*/
   tcph_res2:2;
unsigned short int   tcph_win;
unsigned short int   tcph_chksum;
unsigned short int   tcph_urgptr;
};

int raw_socket;

// creating the raw socket
raw_socket = socket(PF_INET, SOCK_RAW, IPPROTO_TCP);
if(raw_socket < 0){
    fprintf(stderr, "Failed to create the socket\n");
    exit(INTERNAL_ERROR);
}

// datagram to represent the packet
char datagram[4096];

// we need to map it so the datagram can represent it
struct ipheader* iph = (struct ipheader*) datagram;
struct tcpheader* tcph = (struct tcpheader*) datagram + sizeof(ipheader);
struct sockaddr_in sin;

// set the source parameters
sin.sin_family = AF_INET;
sin.sin_port = htons(order_num);    // destination port num
sin.sin_addr.s_addr = inet_addr("172.217.23.196");    // destination ip

// zero out the buffer
memset(datagram, 0, 4096);

// filling in the ip header
iph->iph_ihl = 5;
iph->iph_ver = 4;
iph->iph_tos = 0;
iph->iph_len = sizeof(struct ipheader) + sizeof(struct tcpheader);
iph->iph_ident = htonl(54321); // this dosn't matter
iph->iph_offset = 0;
iph->iph_ttl = 255;
iph->iph_protocol = 6;
iph->iph_chksum = 0;

// setting the source and destination
iph->iph_sourceip = inet_addr("147.229.206.115");
iph->iph_destip = sin.sin_addr.s_addr;

// setting the tcph header
tcph->tcph_srcport = htons(5678);
tcph->tcph_destport = htons(20);
tcph->tcph_seqnum = random();
tcph->tcph_acknum = 0;
tcph->tcph_res2 = 0;
tcph->tcph_offset = 0;
tcph->tcph_syn = TH_FIN;
tcph->tcph_win = htonl(65535);
tcph->tcph_chksum = 0;
tcph->tcph_urgptr = 0;

// calculate the checksum
iph->iph_chksum = 0;//csum((unsigned short *) datagram, iph->iph_len >> 1);

// we need to tell kernel that headers are included in the packet
int one = 1;
const int *val = &one;
if(setsockopt(raw_socket, IPPROTO_IP, IP_HDRINCL, val, sizeof(one)) < 0){
    fprintf(stderr, "Error setting IP_HDRINCL %d\n", errno);
    exit(INTERNAL_ERROR);
}


    // sending the packet
if(sendto(raw_socket, datagram, iph->iph_len, 0, (struct sockaddr *) &sin, sizeof(sin)) < 0){
    fprintf(stderr, "Error while sending %d\n", errno);
    exit(INTERNAL_ERROR);
 }

// close the raw socket
close(raw_socket);

我的问题是，如果我在Wireshark中看不到包裹，如何知道包裹是否已寄出？我在做什么错了？