下面是一段用WinSock编写的程序，请分析后回答问题

#include <stdio.h> 
#include <winsock2.h> 
#include <ws2tcpip.h> 
#define SOURCE_PORT 7234 
#define MAX_RECEIVEBYTE 255 
typedef struct ip_hdr //定义IP首部 
{ 
unsigned char h_verlen; //4位首部长度,4位IP版本号 
unsigned char tos; //8位服务类型TOS 
unsigned short total_len; //16位总长度（字节） 
unsigned short ident; //16位标识 
unsigned short frag_and_flags; //3位标志位 
unsigned char ttl; //8位生存时间 TTL 
unsigned char proto; //8位协议 (TCP, UDP 或其他) 
unsigned short checksum; //16位IP首部校验和 
unsigned int sourceIP; //32位源IP地址 
unsigned int destIP; //32位目的IP地址 
}IPHEADER; 
typedef struct tsd_hdr //定义TCP伪首部 
{ 
unsigned long saddr; //源地址 
unsigned long daddr; //目的地址 
char mbz; 
char ptcl; //协议类型 
unsigned short tcpl; //TCP长度 
}PSDHEADER; 
typedef struct tcp_hdr //定义TCP首部 
{ 
USHORT th_sport; //16位源端口 
USHORT th_dport; //16位目的端口 
unsigned int th_seq; //32位序列号 
unsigned int th_ack; //32位确认号 
unsigned char th_lenres; //4位首部长度/6位保留字 
unsigned char th_flag; //6位标志位 
USHORT th_win; //16位窗口大小 
USHORT th_sum; //16位校验和 
USHORT th_urp; //16位紧急数据偏移量 
}TCPHEADER; 
//CheckSum:计算校验和的子函数 
USHORT checksum(USHORT *buffer, int size) 
{ 
unsigned long cksum=0; 
while(size >1) 
{ 
cksum+=*buffer++; 
size -=sizeof(USHORT); 
} 
if(size ) 
{ 
cksum += *(UCHAR*)buffer; 
} 
cksum = (cksum >> 16) + (cksum & 0xffff); 
cksum += (cksum >>16); 
return (USHORT)(~cksum); 
} 
void useage() 
{ 
printf("******************************************\n"); 
printf("TCPPing\n"); 
printf("Useage: TCPPing.exe Target_ip Target_port \n"); 
printf("*******************************************\n"); 
} 
int main(int argc, char* argv[]) 
{ 
WSADATA WSAData; 
SOCKET sock; 
SOCKADDR_IN addr_in; 
IPHEADER ipHeader; 
TCPHEADER tcpHeader; 
PSDHEADER psdHeader; 
char szSendBuf[60]={0}; 
BOOL flag; 
int rect,nTimeOver; 
useage(); 
if (argc!= 3) 
{ return false; } 
if (WSAStartup(MAKEWORD(2,2), &WSAData)!=0) 
{ 
printf("WSAStartup Error!\n"); 
return false; 
} 
if ((sock = WSASocket(AF_INET,SOCK_RAW,IPPROTO_RAW,NULL,0,WSA_FLAG_OVERLAPPED))
==INVALID_SOCKET) 
{ 
     printf("Socket Setup Error!\n"); 
     return false; 
} 
flag=true; 
if (setsockopt(sock,IPPROTO_IP, IP_HDRINCL,(char *)&flag,sizeof(flag))
==SOCKET_ERROR) 
{ 
     printf("setsockopt IP_HDRINCL error!\n"); 
     return false; 
} 
nTimeOver=1000; 
if (setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (char*)&nTimeOver, 
sizeof(nTimeOver))==SOCKET_ERROR) 
{ 
    printf("setsockopt SO_SNDTIMEO error!\n"); 
    return false; 
} 
addr_in.sin_family=AF_INET; 
addr_in.sin_port=htons(atoi(argv[2])); 
addr_in.sin_addr.S_un.S_addr=inet_addr(argv[1]); 
// 
// 
//填充IP首部 
ipHeader.h_verlen=(4<<4 | sizeof(ipHeader)/sizeof(unsigned long)); 
// ipHeader.tos=0; 
ipHeader.total_len=htons(sizeof(ipHeader)+sizeof(tcpHeader)); 
ipHeader.ident=1; 
ipHeader.frag_and_flags=0; 
ipHeader.ttl=128; 
ipHeader.proto=IPPROTO_TCP; 
ipHeader.checksum=0; 
ipHeader.sourceIP=inet_addr("本地地址"); 
ipHeader.destIP=inet_addr(argv[1]); 
//填充TCP首部 
tcpHeader.th_dport=htons(atoi(argv[2])); 
tcpHeader.th_sport=htons(SOURCE_PORT); //源端口号 
tcpHeader.th_seq=htonl(0x12345678); 
tcpHeader.th_ack=0; 
tcpHeader.th_lenres=(sizeof(tcpHeader)/4<<4|0); 
tcpHeader.th_flag=2; //修改这里来实现不同的标志位探测，2是SYN，1是FIN，16是ACK探测 等等 
tcpHeader.th_win=htons(512); 
tcpHeader.th_urp=0; 
tcpHeader.th_sum=0; 
psdHeader.saddr=ipHeader.sourceIP; 
psdHeader.daddr=ipHeader.destIP; 
psdHeader.mbz=0; 
psdHeader.ptcl=IPPROTO_TCP; 
psdHeader.tcpl=htons(sizeof(tcpHeader)); 
//计算校验和 
memcpy(szSendBuf, &psdHeader, sizeof(psdHeader)); 
memcpy(szSendBuf+sizeof(psdHeader), &tcpHeader, sizeof(tcpHeader)); 
tcpHeader.th_sum=checksum((USHORT *) szSendBuf,sizeof(psdHeader) + sizeof(tcpHeader)); 
memcpy(szSendBuf, &ipHeader, sizeof(ipHeader)); 
memcpy(szSendBuf+sizeof(ipHeader), &tcpHeader, sizeof(tcpHeader)); 
memset(szSendBuf+sizeof(ipHeader)+sizeof(tcpHeader), 0, 4); 
ipHeader.checksum=checksum((USHORT *)szSendBuf, sizeof(ipHeader)+sizeof(tcpHeader)); 
memcpy(szSendBuf, &ipHeader, sizeof(ipHeader)); 
rect=sendto(sock, szSendBuf, sizeof(ipHeader)+sizeof(tcpHeader), 
0, (struct sockaddr*)&addr_in, sizeof(addr_in)); 
if (rect==SOCKET_ERROR) 
{ 
    printf("send error!:%d\n",WSAGetLastError()); 
    return false; 
} 
else 
    printf("send ok!\n"); 
closesocket(sock); 
WSACleanup(); 
return 0; 
}