Linux服务器编程

Question

我从Andy Tanenbaum的书里得到了这个代码。我正在试着运行它。它编译并等待连接。但是当我输入localhost:886时，我在浏览器或终端中都看不到任何效果。(它应该根据代码回显一个新的连接字符串)。

#define     SERVER_PORT         886     /* The port at which the server listens */
#define     BUF_SIZE        64032       /* The size of buffer for request and response */
#define     QUEUE_SIZE      10      /* Block transfer size */


int main (int argc, char* argv[]) {

    int     sock = 0, bnd = 0, lst = 0, fd = 0, sa = 0, bytes = 0, on = 1, conn_count = 0;
    char    buf[BUF_SIZE];
    struct  sockaddr_in channel;            /* IP address holder */

    /* The address structure that binds with the socket */

    memset (&channel, 0, sizeof(channel));

    channel.sin_family      =   AF_INET;
    channel.sin_addr.s_addr     =   htonl (INADDR_ANY);
    channel.sin_port        =   htons (SERVER_PORT);

    /* Parital opening of the socket, while waiting for connection */

    sock                =   socket (AF_INET, SOCK_STREAM, IPPROTO_TCP); /* Creates a new socket */
    if (sock < 0)
        printf ("Partial opening of the socket failed! Error: %d", sock);

    setsockopt (sock, SOL_SOCKET, SO_REUSEADDR, (char *) &on, sizeof(on));

    bnd             =   bind (sock, (struct sockaddr *) &channel, sizeof(channel));
    if (bnd < 0)
        printf ("Binding failure! Error: %d", bnd);

    lst             =   listen (sock, QUEUE_SIZE);
    if (lst < 0)
        printf ("Unable to listen on the socket! Error: %d", lst);

    /* The socket has been set-up. Wait for the connection and process it. */

    while (1) {

        conn_count      +=  1;
        printf ("Received connection: %d", conn_count); 
        sa          =   accept (sock, 0, 0);
        if (sa < 0)
            puts ("Unable to accept the socket opened for connection.");

        read (sa, buf, BUF_SIZE);

        puts (buf);     /* Output the string to the screen */

        close (sa);
    }
}

Answer 1

您是否以sudo/root身份运行此应用程序？您的bind()可能会失败，因为它正在使用特权端口。

来自评论的更新：

特权端口是1024以下的所有端口。

Answer 2

尝试将换行符'\n‘放在您的

 printf ("Received connection: %d\n", conn_count); 

线路。

否则，不会直接刷新stdout，您将什么也看不到。

Answer 3

与其使用printf()和stdout，不如尝试将所有输出更改为没有缓冲的fprintf()和stderr……我也会对错误消息执行同样的操作，以便它们在被调用时立即输出，而不是由stdout缓冲。

最后，如果您想了解错误消息的含义，可以使用带有错误号的strerror()。所以你可以这样做：

if (bnd < 0)
{
    fprintf(stderr, "Binding failure! Error: %s", strerror(bnd));
    exit(1);
}

确保对于strerror()，您还在代码模块开头的某个位置执行了include<string.h>。