我已經編寫了一個程序來接受Linux 2.6.14機器的TCP套接字連接(下面的服務器和客戶機代碼)。我的設計是爲了忽略一些(套接字)輸入並回應其他人。問題是,對於我編寫的代碼,當我忽略(不響應)時,我的select(2)
函數看不到更多數據。爲什麼我的套接字接口在select()調用中停止註冊?
所以在下面的例子中,只要我發送一個t
命令,服務器似乎停止聽取端口實例的操作。直到發送t
命令爲止,服務器將以其Ok.
響應。服務器代碼不會被凍結,因爲它將接受新的端口實例,並且fork(2)
,但它未對t
(測試)命令做出響應的端口仍然看起來凍結。爲什麼是這樣?
這裏是我有用捕獲輸出的嘗試......
~/test$ ./client-test 192.168.20.171 48884
Ok.
Ok.
Ok.t
^Z
[1]+ Stopped ./client-test 192.168.20.171 48884
~/test$ ./client-test 192.168.20.171 48884
Ok.
Ok.
這裏是(去除錯誤代碼和#include
S)爲我的服務器代碼:
#define PORT_NUM 48884
#define CLIENT_CMD_LENGTH 256
static void dostuff(int fd)
{
char buf[CLIENT_CMD_LENGTH];
char bye[] = "Bye!", ok[] = "Ok.";
const struct timeval wait_tv = { .tv_usec = 1000000/20, .tv_sec = 0 };
fd_set read_fd;
do
{
struct timeval tv;
int n;
tv = wait_tv;
FD_ZERO(& read_fd);
FD_SET(fd, &read_fd);
if (select(fd+1, &read_fd, NULL, NULL, &tv)==-1)
{
/* error */
}
else if (FD_ISSET(fd, & read_fd))
{
printf(".\n");
FD_CLR(fd, & read_fd);
n = read(fd,buf, (sizeof buf) - 1);
switch (* buf)
{
case 'q': write(fd,bye,sizeof bye);
return;
case 't': break; /* Ignore */
default: write(fd, ok, sizeof ok);
break;
}
}
} while (1);
return;
}
static void server_work(void)
{
int sockfd;
socklen_t clilen;
struct sockaddr_in serv_addr, cli_addr;
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0) return;
memset((char *) &serv_addr, '\0', sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(PORT_NUM);
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
return;
}
listen(sockfd,5);
clilen = sizeof(cli_addr);
while (1) {
int newsockfd, pid;
newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
continue;
pid = fork();
if (pid < 0)
break;
if (pid == 0) {
close(sockfd);
dostuff(newsockfd);
exit(0);
}
else close(newsockfd);
} /* end of while */
close(sockfd);
return; /* we never get here */
}
int main(int argc, char *argv[]) {
server_work();
return 0;
}
和我的測試客戶端。 ..
void error(const char *msg)
{
perror(msg);
exit(0);
}
int main(int argc, char *argv[])
{
int sockfd, portno, n;
struct sockaddr_in serv_addr;
struct hostent *server;
char buffer[256];
if (argc < 3) {
fprintf(stderr,"usage %s hostname port\n", argv[0]);
exit(0);
}
portno = atoi(argv[2]);
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
server = gethostbyname(argv[1]);
if (server == NULL) {
fprintf(stderr,"ERROR, no such host\n");
exit(0);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr,
(char *)&serv_addr.sin_addr.s_addr,
server->h_length);
serv_addr.sin_port = htons(portno);
if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)
error("ERROR connecting");
do {
bzero(buffer,256);
fgets(buffer,255,stdin);
n = write(sockfd,buffer,strlen(buffer));
if (n < 0)
error("ERROR writing to socket");
bzero(buffer,256);
n = read(sockfd,buffer,255);
if (n < 0)
error("ERROR reading from socket");
printf("%s",buffer);
} while (*buffer != 'B');
close(sockfd);
return 0;
}
當你用select()代碼遍歷代碼時,你會發現什麼情況?你的代碼是否掛起,還是繼續?是否接收到t的選擇超時? – 2011-12-14 03:03:23