Check connection open or closed ?(in C in Linux)

c, linux, network-programming, sockets

Solution

I use send() instead write() that handle no signal :

bzero(buffer, MAX_SIZE_BUFFER);
n = read(sockfd, buffer, MAX_SIZE_BUFFER - 1);
printf("after read%d\n", n);
if (n <= 0)
{
    break;
}
n2 = send(newsockfd, buffer, n, MSG_NOSIGNAL);
if (n2 == -1)
{
    close(sockfd);
    close(newsockfd);
    return;
}
if (n2 != n)
{
    break;
}

Problem

In socket programming in Linux I need to write data in socket but I don't know socket is open or close . how to I know that socket is open and close without read ? ``` printf("befor read%d\n", n); bzero(buffer, MAX_SIZE_BUFFER); n = read(sockfd, buffer, MAX_SIZE_BUFFER - 1); printf("after read%d\n", n); if (n <= 0) { break; } printf("befor write%d, s: %d \n", n , sockfd); n = write(newsockfd, buffer, n); if (n <= 0) { break; } ``` I read from sockfd and I sure this connection is open . When to write buffer in newsockfd I don't know newsockfd is open or close how to check newsockfd is closed ? I know problem . in middle of writing connection closed . for example write 1024 data in 500 connection closed and program closed. how to avoid this ?

Original source