名字与地址转换getservbyname 与 getservbyport函数
名字與地址轉(zhuǎn)換getservbyname 與 getservbyport函數(shù)
服務(wù)也通常靠名字來標(biāo)志，getservbyname函數(shù)用于根據(jù)給定名字查找相應(yīng)服務(wù)。
#include
struct????servent *getservbyname( const char *servname, const char *protoname );
成功：返回servent類型非空指針；
失敗：空指針；
本函數(shù)返回非空指針
struct????servent
{
??????char??????*s_name;??????????//????服務(wù)的正是名字
??????char??????**s_aliases;??????//????別名列表
??????int???????s_port;???????????//????服務(wù)端口號
??????char??????*s_proto;?????????//????使用的協(xié)議
};
服務(wù)名參數(shù)servname必須指定。如果同時指定了協(xié)議（即protoname參數(shù)為非空指針），那么指定的服務(wù)必須有匹配的協(xié)議。有些因特網(wǎng)服務(wù)既用于TCP也用于UDP提供（如DNS）。如果protoname沒有指定而servname指定服務(wù)支持多個協(xié)議，那么返回那個端口號取決于實(shí)現(xiàn)。一般來說，支持多個協(xié)議的服務(wù)旺旺使用相同的TCP端口號和UDP端口號。
servent結(jié)構(gòu)中關(guān)心的主要是端口號。
注意：該端口號是以網(wǎng)絡(luò)字節(jié)的順序返回的，因此把它存放到套接口地質(zhì)結(jié)構(gòu)時絕對不能調(diào)用htons。
函數(shù)getservbyport用于根據(jù)給定端口號和可選協(xié)議查找相應(yīng)的服務(wù)。
#include
struct????servent *getservbyport( int port, const char *protoname );
成功：返回servent類型非空指針；
失敗：空指針；
注意： port的值必須為網(wǎng)絡(luò)字節(jié)序，如：
ptr = getservbyport( htons(53), "udp");?????// DNS using UDP
?
示例代碼：
int main(int argc, char** argv)
{
????int sockFd,n;
????char recvLine[MAXLINE + 1], addrStr[128],str[INET_ADDRSTRLEN];;
????char **charpptr;
????struct sockaddr_in servAddr;
????struct in_addr **pptr;
????struct in_addr *inetAddrP[2];
????struct in_addr inetAddr;
????struct hostent *hptr;
????struct servent *sptr;
????if(argc != 3)
????{
????????ReportError("Usage : GetService ");
????????exit(1);
????}
????if((hptr = gethostbyname(argv[1])) == NULL)
????{
????????if(inet_aton(argv[1], &inetAddr) == 0)
????????{
????????????ReportError("hostName error for %s : %s",argv[1],hstrerror(h_errno));
????????????exit(1);
????????}
????????else
????????{
????????????inetAddrP[0] = &inetAddr;
????????????inetAddrP[1] = NULL;
????????????pptr = inetAddrP;
????????}
????}
????else?//先打印host信息
????{
????????printf("Official hostname : %s\n",hptr->h_name);
????????for(charpptr=hptr->h_aliases; *charpptr!=NULL; ++charpptr)
????????????printf("\tAlias : %s\n",*charpptr);
????????switch(hptr->h_addrtype)
????????{
????????????case AF_INET:
????????????????for(charpptr = hptr->h_addr_list; *charpptr!=NULL; ++charpptr)
????????????????????printf("\tAddress : %s\n",
???????????????????????????inet_ntop(hptr->h_addrtype, *charpptr, str, sizeof(str)));
????????????????break;
????????}
????????pptr = (struct in_addr**)hptr->h_addr_list;
????}
????if( (sptr = getservbyname(argv[2], "tcp")) == NULL)
????{
????????ReportError("getservbyname error for %s",argv[2]);
????????exit(1);
????}
????printf("Official service name : %s\n",sptr->s_name);//打印service信息
????for(charpptr=sptr->s_aliases; *charpptr!=NULL; ++charpptr)
????????printf("\tAlias : %s\n",*charpptr);
????printf("\tPort number : %d\n",sptr->s_port);
????printf("\tprotocol : %s\n",sptr->s_proto);
????for(; *pptr != NULL; ++pptr)
????{
????????if((sockFd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
????????{
????????????ReportError("socket error");
????????????exit(1);
????????}
????????bzero(&servAddr, sizeof(servAddr));
????????servAddr.sin_family = AF_INET;
????????servAddr.sin_port = sptr->s_port;//根據(jù)獲取的服務(wù)信息設(shè)置端口號
????????memcpy(&servAddr.sin_addr, *pptr, sizeof(struct in_addr));//根據(jù)hostname信息設(shè)置IP
????????inet_ntop(AF_INET, (struct sockaddr*)&servAddr, addrStr,sizeof(servAddr));
????????printf("trying %s : %d\n", addrStr, servAddr.sin_port);
????????if(connect(sockFd, (struct sockaddr*)&servAddr, sizeof(servAddr)) == 0) //連接成功
????????????break;
????????ReportError("connect error");
????????close(sockFd);
????}
????if(*pptr == NULL)
????{
????????ReportError("unable to connet");
????????exit(1);
????}
????while( (n=read(sockFd, recvLine, MAXLINE)) > 0)
????{
????????recvLine[n] = 0;
????????fputs(recvLine, stdout);
????}
????return 0;
}
?
?
?
連接被拒絕，不知道什么原因，難道是相應(yīng)的服務(wù)沒開啟？
用service --status-all命令可以查看那當(dāng)前運(yùn)行的服務(wù)及其狀態(tài)
[root@localhost bin]# service --status-all
abrtd (pid??1979) 正在運(yùn)行...
abrt-dump-oops (pid 1987) 正在運(yùn)行...
acpid (pid??1801) 正在運(yùn)行...
atd (pid??2006) 正在運(yùn)行...
auditd (pid??1679) 正在運(yùn)行...
avahi-daemon (pid??1775) 正在運(yùn)行...
用法：/etc/init.d/bluetooth {start|stop}
Stopped
cgred 已停
cpuspeed 已停
crond (pid??1995) 正在運(yùn)行...
dnsmasq 已停
用法：/etc/init.d/firstboot {start|stop}
hald (pid??1810) 正在運(yùn)行...
httpd 已停
表格：filter
Chain INPUT (policy ACCEPT)
num??target?????prot opt source???????????????destination????????
1????ACCEPT?????all??????::/0?????????????????::/0????????????????state RELATED,ESTABLISHED
2????ACCEPT?????icmpv6????::/0?????????????????::/0???????????????
3????ACCEPT?????all??????::/0?????????????????::/0???????????????
4????ACCEPT?????tcp??????::/0?????????????????::/0????????????????state NEW tcp dpt:22
5????REJECT?????all??????::/0?????????????????::/0????????????????reject-with icmp6-adm-prohibited
Chain FORWARD (policy ACCEPT)
num??target?????prot opt source???????????????destination????????
1????REJECT?????all??????::/0?????????????????::/0????????????????reject-with icmp6-adm-prohibited
Chain OUTPUT (policy ACCEPT)
num??target?????prot opt source???????????????destination????????
表格：filter
Chain INPUT (policy ACCEPT)
num??target?????prot opt source???????????????destination????????
1????ACCEPT?????all??--??0.0.0.0/0????????????0.0.0.0/0???????????state RELATED,ESTABLISHED
2????ACCEPT?????icmp --??0.0.0.0/0????????????0.0.0.0/0??????????
3????ACCEPT?????all??--??0.0.0.0/0????????????0.0.0.0/0??????????
4????ACCEPT?????tcp??--??0.0.0.0/0????????????0.0.0.0/0???????????state NEW tcp dpt:22
5????REJECT?????all??--??0.0.0.0/0????????????0.0.0.0/0???????????reject-with icmp-host-prohibited
Chain FORWARD (policy ACCEPT)
num??target?????prot opt source???????????????destination????????
1????REJECT?????all??--??0.0.0.0/0????????????0.0.0.0/0???????????reject-with icmp-host-prohibited
Chain OUTPUT (policy ACCEPT)
num??target?????prot opt source???????????????destination????????
irqbalance 已停
Kdump is not operational
mdmonitor (pid??1733) 正在運(yùn)行...
messagebus (pid??1752) 正在運(yùn)行...
模塊 netconsole 未被加載
配置設(shè)備：
lo eth0
當(dāng)前的活躍設(shè)備：
lo eth0
NetworkManager (pid??1763) 正在運(yùn)行...
ntpd 已停
master (pid??1955) 正在運(yùn)行...
進(jìn)程記帳被禁用。
quota_nld 已停
rdisc 已停
restorecond (pid 2781) 正在運(yùn)行...
rngd 已停
rsyslogd (pid??1695) 正在運(yùn)行...
sandbox is stopped
saslauthd 已停
smartd 已停
openssh-daemon (pid??1879) 正在運(yùn)行...
wpa_supplicant (pid??1812) 正在運(yùn)行...
轉(zhuǎn)載于:https://www.cnblogs.com/rexienk/p/4856079.html
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