我正在尝试一个FTP客户端，该客户端可以连接到多个服务器（用于错误编码），但是我认为我做错了什么。 当前，我正在使用connect（）测试远程服务器以查看它们是否可用。但是，对于所有服务器（无论它们是否可用），select的返回都是正确的。
客户端可以通过配置文件访问服务器ip：port
struct server
{
char address[13];
char port[6];
int status;
int sd;
};
typedef struct deployment
{
int n;
int k;
unsigned int block_size;
struct server server_list[MAX_SERVERS];
} Config;
示例config.txt
3
2
4096
127.0.0.1:13567
127.0.0.1:13568
127.0.0.1:13569
Here, I a loop through n servers and try to connect. Then, have select handle the rest of the program. However, select is returning true for all ports if I use &write_fds and returning the OPPOSITE (i.e all unavailable ports) using &read_fds. I suspect using connect is incorrect and I need to getsockopt? I am really not sure about what needs to be done here or what would be a best practice. Picture of output In this example, I only have 1 server running so the other 2 connect calls return errors yet select doesn't seem to pick up on it.
for (int i = 0; i < settings->n; i++)
{
// get address and port
int port = atoi(settings->server_list[i].port);
settings->server_list[i].sd = socket(AF_INET, SOCK_STREAM, 0);
struct sockaddr_in server_addr;
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = inet_addr(settings->server_list[i].address);
server_addr.sin_port = htons(port);
//connect to server
settings->server_list[i].status = connect(settings->server_list[i].sd, (struct sockaddr *)&server_addr, sizeof(server_addr));
if (settings->server_list[i].status < 0)
{
printf("Error: %s (Errno:%d)\n", strerror(errno), errno);
}
max_sd = max(max_sd, settings->server_list[i].sd);
}
while (1)
{
FD_ZERO(&read_fds);
FD_ZERO(&write_fds);
for (int i = 0; i < settings->n; i++)
{
FD_SET(settings->server_list[i].sd, &read_fds);
FD_SET(settings->server_list[i].sd, &write_fds);
}
select(max_sd + 1, &read_fds, NULL, NULL, NULL);
select(max_sd + 1, NULL, &write_fds, NULL, NULL);
// LIST_REQUEST
if (packet->type == (unsigned char)0xA1)
{
for (int i = 0; i < settings->n; i++)
{
if (FD_ISSET(settings->server_list[i].sd, &write_fds))
{
printf("SELECTED:\n");
printf("Address: %s\t", settings->server_list[i].address);
printf("Port: %s\t", settings->server_list[i].port);
printf("Sd: %d\t", settings->server_list[i].sd);
printf("Connection Status: %d\n", settings->server_list[i].status);
}
}
}
// GET_REQUEST
if (packet->type == (unsigned char)0xB1)
{
printf("GET REQUEST!\n");
}
// PUT_REQUEST
if (packet->type == (unsigned char)0xC1)
{
printf("PUT REQUEST!\n");
}
exit(0);
}
If anyone could shed some light on what I need to be doing it would be greatly appreciated. I've tried to research as best I can including this post: Using select() for non-blocking sockets to connect always returns 1 but still don't understand what I need to do given my circumstances. Thanks so much.
