连接一个没有监听的端口结果会怎样

一句话总结：消息可达的情况下服务端直接抛个RST过来

服务端：

#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;}

看结果，客户端发送syn给服务端，服务端直接回了个RST。