我尝试解析主机名,然后打开/关闭主机的套接字。
以下代码运行正常。我遇到的问题是连接似乎没有正确关闭。我留下了一堆TIME_WAITS:
tcp 0 0 192.168.142.139:44475 172.217.23.14:443 TIME_WAIT
tcp 0 0 192.168.142.139:44362 45.79.5.162:80 TIME_WAIT
tcp 0 0 192.168.142.139:44373 45.79.5.162:80 TIME_WAIT
tcp 0 0 192.168.142.139:44461 172.217.23.14:443 TIME_WAIT
tcp 0 0 192.168.142.139:44468 172.217.23.14:443 TIME_WAIT
tcp 0 0 192.168.142.139:44472 172.217.23.14:443 TIME_WAIT
tcp 0 0 192.168.142.139:44474 172.217.23.14:443 TIME_WAIT
tcp 0 0 192.168.142.139:44459 172.217.23.14:443 TIME_WAIT
tcp 0 0 192.168.142.139:44470 172.217.23.14:443 TIME_WAIT
tcp 0 0 192.168.142.139:44463 172.217.23.14:443 TIME_WAIT
tcp 0 0 192.168.142.139:44464 172.217.23.14:443 TIME_WAIT
我并不特别需要向主持人发送任何特定内容,这更像是一般的互联网检查。我也尝试过使用非阻塞连接,然后选择select。结果相同。
int port = 443;
char *hostname = "google.com";
int open_socket(char *ip)
{
int error = 0; // Socket error
struct sockaddr_in address;
short int sock = -1;
fd_set fdset;
struct timeval tv;
int so_keepalive = 0;
sock = socket(PF_INET, SOCK_STREAM , 0);
if (sock < 0)
return 150;
address.sin_family = AF_INET;
address.sin_addr.s_addr = inet_addr(ip);
address.sin_port = htons(port);
/* address.sin_addr.s_addr = INADDR_ANY; */
FD_ZERO(&fdset);
FD_SET(sock, &fdset);
tv.tv_sec = 3;
tv.tv_usec = 0;
int yes = 1;
// setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int));
// setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv, sizeof(struct timeval));
setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (char *)&tv, sizeof(struct timeval));
setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, &so_keepalive, sizeof(so_keepalive));
if (connect(sock, (struct sockaddr *)&address , sizeof(address)) < 0)
error = 150;
if (error == 0) {
char *message = "HELLO";
if (send(sock , message , strlen(message) , 0) < 0)
error = 180;
char server_reply[2000];
if( recv(sock, server_reply , 2000 , 0) < 0)
error = 190;
}
/* shutdown(sock, SHUT_RDWR); */
close(sock);
return error;
}
int connection_check()
{
struct addrinfo *result;
struct in_addr addr;
int error;
error = getaddrinfo(hostname, NULL, NULL, &result);
if (error != 0)
{
fprintf(stderr, "DNS Lookup Failed: %s\n", gai_strerror(error));
return 100;
}
addr.s_addr = ((struct sockaddr_in *)(result->ai_addr))->sin_addr.s_addr;
printf("\nUsing %s for internet check\n", inet_ntoa(addr));
freeaddrinfo(result);
return(open_socket(inet_ntoa(addr)));
}
有人可以建议我应该如何正确处理这个问题。
答案 0 :(得分:0)
TCP要求关闭连接的端点进一步阻塞 连接在同一主机/端口对上,直到没有来自的数据包 该连接保留在网络中。
要临时阻止连接,一个端点会保留TCP的副本 控制块(TCB),表示连接已终止 最近。这种连接处于TIME-WAIT状态。连接在 TIME-WAIT被移至CLOSED并且足够后丢弃它们的TCB 时间已过,来自同一连接的所有数据包都已离开 网络。数据包通过到达其中一个网络离开网络 终点和被拒绝,或者到期时间到期 路由器上的(TTL)字段并被删除。