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;
#endiflog = 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);}}}
#endifif (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

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