what is the return value of sockect close() function

[policeman0077]

I am new to socket programming.

what is the return value of sockect close() function. I could not find in https://docs.espressif.com/projects/esp ... light=lwip.

I always get -1 as return of close(). I have SO_REUSEADDR enabled. Is it safe to reconnect use the same sock after I call close()? Would lwip reuse the sock I just close().

Thank you for any input.

here is the code i wrote:

Code: Select all

int tcp_socket_close(asl_socket_t *s)
{
    int ret=0;
    ret = shutdown(s->socketfd,SHUT_WR);//close write, send fin
    if(ret<0)
    {
        ESP_LOGE(TAG, "tcp_socket_close:fail to SHUT_WR");
    }
    ret = shutdown(s->socketfd,SHUT_RD);//close read
    if(ret<0)
    {
        ESP_LOGE(TAG, "tcp_socket_close:fail to SHUT_RD");
        //return ret;
    }
    
    ret = close(s->socketfd);//destroy socket
    ESP_LOGI(TAG, "tcp_socket_close: close() return:%d",ret);
    return ret;
}

I used to check return of socket close() but is always return -1

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int tcp_socket_reconnect(asl_socket_t *s)
{
    int ret=0;
    ret=tcp_socket_close(s);
    // if(ret<0)
    // {
    //     ESP_LOGI(TAG, "tcp_socket_reconnect:fail to close socket");
    //     //esp_restart();//fail to close the socket restart
    //     return ret;
    // }
    ret=tcp_socket_connect();
    return ret;
}

[ESP_Sprite]

Close is a posix function; if it returns -1, there has been an error. I think you can do this to get the specifics:

Code: Select all

#include <stdio.h>

[...]

if (close(..)==-1) {
	perror("close");
}

[policeman0077]

Close is a posix function; if it returns -1, there has been an error. I think you can do this to get the specifics:

Code: Select all

#include <stdio.h>

[...]

if (close(..)==-1) {
	perror("close");
}

Thank you. I will try your code.