一句話總結：訊息可達的情況下服務端直接拋個RST過來

服務端：

#include <iostream>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>

using namespace std;
int main()
{
	struct sockaddr_in serAddr;
	int listenSock, cnntSock;
	listenSock = socket(AF_INET, SOCK_STREAM, 0);
	serAddr.sin_family = AF_INET;
	serAddr.sin_addr.s_addr = INADDR_ANY;
	serAddr.sin_port = htons(1248);

	bind(listenSock, (const struct sockaddr *)&serAddr, sizeof(sockaddr_in));
	listen(listenSock, 10);

	struct sockaddr_in cliAddr;
	socklen_t len = sizeof(sockaddr_in);
	cnntSock = accept(listenSock, (struct sockaddr*)&cliAddr, &len);
	cout<< "IP:" <<inet_ntoa(cliAddr.sin_addr) <<", port:"<<cliAddr.sin_port<<endl;
	unsigned int total = 0;
	while(1)
	{
		getchar();
		cout <<"read msg..."<<endl;
		char buf[6000] = {0};
		int ret = recv(cnntSock, buf, sizeof(buf), 0);
		total += ret;
		cout << "msg:" <<endl;
		cout << buf;
		cout << "recv msg size:" << ret << "total size:" << total <<endl;
		break;
	}
	close(cnntSock);
	close(listenSock);
	return 0;
}
 

看結果，客戶端傳送syn給服務端，服務端直接回了個RST。