lwip获取socket的状态

在lwIP中，可以使用`netconn_get_info()`函数来获取一个连接（socket）的状态信息。该函数的定义如下：

err_t netconn_get_info(struct netconn *conn, struct netconn_info *info);

其中，`conn`参数是一个指向`struct netconn`类型的指针，表示要获取信息的连接；`info`参数是一个指向`struct netconn_info`类型的指针，用于存储获取到的连接信息。

`struct netconn_info`类型定义如下：

struct netconn_info {
    u16_t pcb_type;             /* protocol control block type (TCP/UDP) */
    u16_t local_port;           /* local port */
    u16_t remote_port;          /* remote port */
    ip_addr_t local_ip;         /* local IP address */
    ip_addr_t remote_ip;        /* remote IP address */
    u8_t used;                  /* whether the pcb is used or not */
    u8_t state;                 /* TCP state or UDP PCB state */
    u32_t rcv_wnd;              /* receive window */
    u32_t rcv_queued;           /* receive queued */
    u32_t snd_queued;           /* send queued */
    u32_t acked;                /* ACKed */
    u32_t unacked;              /* UnACKed */
    u32_t last_ack;             /* Last ACKed */
    u32_t last_rcv_ack;         /* Last ACK sent */
    u32_t last_rcv_wnd;         /* Last receive window */
    u32_t total_rx;             /* Total received */
    u32_t total_tx;             /* Total transmitted */
    u32_t err_tx;               /* Transmit errors */
    u32_t err_rx;               /* Receive errors */
    u32_t err_connect;          /* Connect errors */
    u32_t err_timeout;          /* Timeout errors */
    u32_t err_abrt;             /* Abort errors */
};

在获取连接状态信息后，可以根据`state`字段的值来判断连接的状态。具体的状态值定义在`tcp.h`或`udp.h`中。例如，以下是TCP连接的状态值定义：

/* TCP connection states */
#define CLOSED              0        /* closed */
#define LISTEN              1        /* listening for connection */
#define SYN_SENT            2        /* active, have sent syn */
#define SYN_RCVD            3        /* have sent and received syn */
#define ESTABLISHED         4        /* established */
#define FIN_WAIT_1          5        /* have closed, sent fin */
#define FIN_WAIT_2          6        /* have closed, fin is acked */
#define CLOSE_WAIT          7        /* have closed, remote peer is closing */
#define CLOSING             8        /* closed xchd FIN; await FIN-ACK */
#define LAST_ACK            9        /* had fin and close; await FIN-ACK */
#define TIME_WAIT           10       /* in 2*msl quiet wait after close */

因此，可以通过判断`state`字段的值来确定连接的状态，进而进行相应的处理。