从Nginx绑定80端口学套接字编程
《UNIX网络编程(卷1)：套接字联网API(第3版)》
ngx_connection.c
ngx_int_t
ngx_open_listening_sockets(ngx_cycle_t *cycle)
{
int reuseaddr;
ngx_uint_t i, tries, failed;
ngx_err_t err;
ngx_log_t *log;
ngx_socket_t s;
ngx_listening_t *ls;
reuseaddr = 1;
#if (NGX_SUPPRESS_WARN)
failed = 0;
#endif
log = cycle->log;
/* TODO: configurable try number */
for (tries = 5; tries; tries--) {
failed = 0;
/* for each listening socket */
ls = cycle->listening.elts;
for (i = 0; i < cycle->listening.nelts; i++) {
if (ls[i].ignore) {
continue;
}
if (ls[i].fd != -1) {
continue;
}
if (ls[i].inherited) {
/* TODO: close on exit */
/* TODO: nonblocking */
/* TODO: deferred accept */
continue;
}
s = ngx_socket(ls[i].sockaddr->sa_family, ls[i].type, 0);
if (s == -1) {
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
ngx_socket_n " %V failed", &ls[i].addr_text);
return NGX_ERROR;
}
if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
(const void *) &reuseaddr, sizeof(int))
== -1)
{
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
"setsockopt(SO_REUSEADDR) %V failed",
&ls[i].addr_text);
if (ngx_close_socket(s) == -1) {
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
ngx_close_socket_n " %V failed",
&ls[i].addr_text);
}
return NGX_ERROR;
}
#if (NGX_HAVE_INET6 && defined IPV6_V6ONLY)
if (ls[i].sockaddr->sa_family == AF_INET6) {
int ipv6only;
ipv6only = ls[i].ipv6only;
if (setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY,
(const void *) &ipv6only, sizeof(int))
== -1)
{
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
"setsockopt(IPV6_V6ONLY) %V failed, ignored",
&ls[i].addr_text);
}
}
#endif
/* TODO: close on exit */
if (!(ngx_event_flags & NGX_USE_AIO_EVENT)) {
if (ngx_nonblocking(s) == -1) {
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
ngx_nonblocking_n " %V failed",
&ls[i].addr_text);
if (ngx_close_socket(s) == -1) {
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
ngx_close_socket_n " %V failed",
&ls[i].addr_text);
}
return NGX_ERROR;
}
}
ngx_log_debug2(NGX_LOG_DEBUG_CORE, log, 0,
"bind() %V #%d ", &ls[i].addr_text, s);
if (bind(s, ls[i].sockaddr, ls[i].socklen) == -1) {
err = ngx_socket_errno;
if (err == NGX_EADDRINUSE && ngx_test_config) {
continue;
}
ngx_log_error(NGX_LOG_EMERG, log, err,
"bind() to %V failed", &ls[i].addr_text);
if (ngx_close_socket(s) == -1) {
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
ngx_close_socket_n " %V failed",
&ls[i].addr_text);
}
if (err != NGX_EADDRINUSE) {
return NGX_ERROR;
}
failed = 1;
continue;
}
#if (NGX_HAVE_UNIX_DOMAIN)
if (ls[i].sockaddr->sa_family == AF_UNIX) {
mode_t mode;
u_char *name;
name = ls[i].addr_text.data + sizeof("unix:") - 1;
mode = (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
if (chmod((char *) name, mode) == -1) {
ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
"chmod() \"%s\" failed", name);
}
if (ngx_test_config) {
if (ngx_delete_file(name) == NGX_FILE_ERROR) {
ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
ngx_delete_file_n " %s failed", name);
}
}
}
#endif
if (listen(s, ls[i].backlog) == -1) {
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
"listen() to %V, backlog %d failed",
&ls[i].addr_text, ls[i].backlog);
if (ngx_close_socket(s) == -1) {
ngx_log_error(NGX_LOG_EMERG, log, ngx_socket_errno,
ngx_close_socket_n " %V failed",
&ls[i].addr_text);
}
return NGX_ERROR;
}
ls[i].listen = 1;
ls[i].fd = s;
}
if (!failed) {
break;
}
/* TODO: delay configurable */
ngx_log_error(NGX_LOG_NOTICE, log, 0,
"try again to bind() after 500ms");
ngx_msleep(500);
}
if (failed) {
ngx_log_error(NGX_LOG_EMERG, log, 0, "still could not bind()");
return NGX_ERROR;
}
return NGX_OK;
}
调试结果：
注意：查看是bind的第二个参数指向特定协议的地址结构的指针是p *(struct sockaddr_in *)(ls[0].sockaddr) 而不是p *(struct sockaddr *)(ls[0].sockaddr)
故意将默认端口改为801看看：
(gdb) p *(struct sockaddr_in *)(ls[i].sockaddr)
$3 = {sin_family = 2, sin_port = 8451, sin_addr = {s_addr = 0}, sin_zero = "\000\000\000\000\000\000\000"}
(gdb) p htons(80)
$4 = 20480
(gdb) p htons(801)
$5 = 8451