TCP带外数据特点:
1,该数据有两种接收方式:
1.默认方式:通过单独缓冲区接收(不是接受端接受其他数据的缓冲区),当带外数据到达时,内核会向接收套接字宿主进程发送SIGURG信号
2.设置为“带内数据”:通过接收端调用setsockopt打开SO_IOOBNLINE选项就可以将带外数据放进”带内缓冲区“,但也可以通过sockatmark判断”带内缓冲区“的位置(每个TCP连接最多只有一个带外标记)
2.当TCP套接字接收到带外数据时,select会返回设置异常集(编程时可利用这一点)
采用SIGURG通知接收端接收带外数据:
#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/socket.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/signal.h>
#include <fcntl.h>
#define BUFSIZE 4096
#define LISTENQ 100
int connfd;
void sig_urg(int signo) {
ssize_t n;
char buf[BUFSIZE];
if ((n = recv(connfd,buf,BUFSIZE - 1,MSG_OOB)) != n) {
printf("recv from peer error: %s\n",strerror(errno));
exit(1);
}
buf[n] = 0;
printf("receive %ld bytes from peer: %s\n",n,buf);
}
int main(int argc,char** argv) {
if (argc != 2) {
printf("please add or check <ip-address or host-name> <service-name or port>\n");
exit(1);
}
struct addrinfo hints;
bzero(&hints,sizeof(struct addrinfo));
hints.ai_flags = AI_PASSIVE;
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
struct addrinfo* results;
int err;
if ((err = getaddrinfo(NULL,argv[1],&hints,&results)) != 0) {
printf("getaddrinfo error: %s\n",gai_strerror(err));
exit(1);
}
struct addrinfo* dummy = results;
int sockfd;
for (; dummy != NULL; dummy = dummy->ai_next) {
if ((sockfd = socket(dummy->ai_family,dummy->ai_socktype,dummy->ai_protocol)) < 0) {
continue;
}
if (bind(sockfd,dummy->ai_addr,dummy->ai_addrlen) == 0) {
break;
}
close(sockfd);
}
if (listen(sockfd,LISTENQ) < 0) {
printf("listen error: %s\n",strerror(errno));
exit(1);
}
char buf[BUFSIZE];
ssize_t n;
for (; ;) {
if ((connfd = accept(sockfd,NULL,NULL)) < 0) {
if (errno == EINTR) {
continue;
}else {
printf("accept error: %s\n",strerror(errno));
exit(1);
}
}
if (signal(SIGURG,sig_urg) == SIG_ERR) {
printf("signal error: %s\n",strerror(errno));
exit(1);
}
if (fcntl(connfd,F_SETOWN,getpid()) < 0) {
printf("fcntl error: %s\n",strerror(errno));
exit(1);
}
while ((n = read(connfd,buf,BUFSIZE - 1)) > 0) {
buf[n] = 0;
printf("read %ld bytes from peer: %s\n",n,buf);
}
}
return 0;
}
采用Select:
#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/socket.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/select.h>
#include <fcntl.h>
#define BUFSIZE 4096
#define LISTENQ 100
int main(int argc,char** argv) {
if (argc != 2) {
printf("please add or check <services-name>\n");
exit(1);
}
struct addrinfo hints;
bzero(&hints,sizeof(struct addrinfo));
hints.ai_flags = AI_PASSIVE;
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
struct addrinfo* results;
int err;
if ((err = getaddrinfo(NULL,argv[1],&hints,&results)) != 0) {
printf("getaddrinfo error: %s\n",gai_strerror(err));
exit(1);
}
struct addrinfo* dummy = results;
int sockfd;
for (; dummy != NULL; dummy = dummy->ai_next) {
if ((sockfd = socket(dummy->ai_family,dummy->ai_socktype,dummy->ai_protocol)) < 0) {
continue;
}
if (bind(sockfd,dummy->ai_addr,dummy->ai_addrlen) == 0) {
break;
}
close(sockfd);
}
if (listen(sockfd,LISTENQ) < 0) {
printf("listen error: %s\n",strerror(errno));
exit(1);
}
int connfd;
fd_set rs;
fd_set es;
if ((connfd = accept(sockfd,NULL,NULL)) < 0) {
printf("accept error: %s\n",strerror(errno));
exit(1);
}
for (; ;) {
FD_ZERO(&rs);
FD_ZERO(&es);
FD_SET(connfd,&rs);
FD_SET(connfd,&es);
if (select(connfd + 1,&rs,NULL,&es,NULL) < 0) {
if (errno == EINTR) {
printf("select: %s\n",strerror(errno));
continue;
}else {
printf("select error: %s\n",strerror(errno));
exit(1);
}
}
if (FD_ISSET(connfd,&rs)) {
char buf[BUFSIZE];
ssize_t n;
if ((n = read(connfd,buf,BUFSIZE - 1)) < 0) {
printf("read error: %s\n",strerror(errno));
exit(1);
}else if (n == 0){
break;
}
buf[n] = 0;
printf("read %ld normal bytes from peer: %s\n",n,buf);
}
if (FD_ISSET(connfd,&es)) {
char buf[BUFSIZE];
ssize_t n;
if ((n = recv(connfd,buf,BUFSIZE - 1,MSG_OOB)) < 0) {
printf("recv from peer error: %s\n",strerror(errno));
exit(1);
}else if (n == 0) {
break;
}
buf[n] = 0;
printf("recv %ld OOB bytes from peer: %s\n",n,buf);
}
}
return 0;
}
将”带外数据“放进”带内缓冲区”,并含有带外标记的接收端:
(最后一种要准确提取带外数据很麻烦,而且有可能会丢失,不建议使用)
#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/socket.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#define BUFSIZE 4096
#define LISTENQ 100
int main(int argc,char** argv) {
if (argc != 2) {
printf("please add or check <services>\n");
exit(1);
}
struct addrinfo hints;
bzero(&hints,sizeof(struct addrinfo));
hints.ai_flags = AI_PASSIVE;
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
struct addrinfo *results;
int err;
if ((err = getaddrinfo(NULL,argv[1],&hints,&results)) != 0) {
printf("getaddrinfo error: %s\n",gai_strerror(err));
exit(1);
}
struct addrinfo* dummy = results;
int sockfd;
for (; dummy != NULL; dummy = dummy->ai_next) {
if ((sockfd = socket(dummy->ai_family,dummy->ai_socktype,dummy->ai_protocol)) < 0) {
continue;
}
if (bind(sockfd,dummy->ai_addr,dummy->ai_addrlen) == 0) {
break;
}
close(sockfd);
}
if (dummy == NULL) {
freeaddrinfo(results);
printf("all socket failed\n");
exit(1);
}
freeaddrinfo(results);
if (listen(sockfd,LISTENQ) < 0) {
printf("listen error: %s\n",strerror(errno));
exit(1);
}
const int on = 1;
if (setsockopt(sockfd,SOL_SOCKET,SO_OOBINLINE,&on,sizeof(on)) < 0) {
printf("setsockopt error: %s\n",strerror(errno));
exit(1);
}
int connfd;
ssize_t n;
char buf[BUFSIZE];
int flag;
for (; ;) {
if ((connfd = accept(sockfd,NULL,NULL)) < 0) {
printf("accept error: %s\n",strerror(errno));
exit(1);
}
while (1) {
if ((flag = sockatmark(connfd)) < 0) {
printf("sockmark error: %s\n",strerror(errno));
exit(1);
}
if ((n = read(connfd,buf,BUFSIZE - 1)) < 0) {
printf("read error: %s\n",strerror(errno));
exit(1);
}else if (n == 0) {
break;
}
if (flag) {
printf("receive %ld OOB bytes from peer %s\n",n,buf);
}else {
printf("receive %ld normal bytes from peer %s\n",n,buf);
}
}
}
return 0;
}