[英]Linux C socket UDP server. Nothing being received by select()
自從我輸入select語句以來,我的UDP服務器接受任何輸入時遇到問題。 目的是等待來自2個不同套接字(具有不同端口)的數據包。 同時,我還希望它能夠告訴服務器何時要將某些內容發送到同步監聽的端口之一。 在下面的代碼中,程序運行直至到達select()
語句,此時,如果我嘗試將某些內容發送到服務器(在本地計算機上),則不接受任何內容,程序掛起,等待。 我也嘗試注釋掉writefds
fd_set及其隨附的FD_ISSET
但是發生了相同的事情。 我已經精疲力盡了,想弄清楚這些東西,所以可能有很多事情是沒有意義的,但是我在當前狀態下盡了最大努力。 我道歉。
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/select.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#define MYPORT "20444" // the port users will be connecting to
#define MAXBUFLEN 1024 //maximum packet length
#define SERVER_R 142.66.140.13 //Server to the "right" of current
#define RTEX_R_PORT "20445" //Port for routing table exchange
typedef enum {false, true} bool;
/*struct to store packet fields into
seq: sequence number;
type: message type; send get ACK
src: client's unique 10 digit number
dst: destination's unique 10 digit number
payload: the message being transferred, if there is any
*/
struct packet
{
char seq[4];
char type[5];
char src[11];
char dst[11];
char payload[MAXBUFLEN];
};
// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
if (sa->sa_family == AF_INET) {
return &(((struct sockaddr_in*)sa)->sin_addr);
}
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int main(void)
{
//rr: reading from server to the "right"
//rw: writing to the server to the "right"
int sockfd, rtex_rr_sockfd, rtex_rw_sockfd, rv, rrr, rrw, numbytes, i, j, first, max_fd;
struct addrinfo hints, *servinfo, *p, *p2, *p3;
struct sockaddr_storage their_addr, right_addr;
fd_set readfds, writefds;
char buf[MAXBUFLEN];
char temp_buf[MAXBUFLEN];
char d_to_s[MAXBUFLEN];
char *field;
socklen_t addr_len;
char s[INET6_ADDRSTRLEN];
FILE *m_storage;
struct packet inet_packet;
static const struct packet EmptyPacket;
static int rt[51][4];
bool re_exists=false;
bool rt_empty=true;
struct timeval tv;
memset(&hints, 0, sizeof hints);//"zero out" the hints struct
hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4
hints.ai_socktype = SOCK_DGRAM;
hints.ai_flags = AI_PASSIVE; // use my IP
//prepare socket address structures and store them in servinfo and store in linked list
if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
// loop through all the results and bind to the first we can
for(p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("listener: socket");
continue;
}
if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
close(sockfd);
perror("listener: bind");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "listener: failed to bind socket\n");
return 2;
}
if ((rrr = getaddrinfo(NULL, RTEX_R_PORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rrr));
return 1;
}
for(p2 = servinfo; p2 != NULL; p2 = p2->ai_next) {
if ((rtex_rr_sockfd = socket(p2->ai_family, p2->ai_socktype,
p2->ai_protocol)) == -1) {
perror("listener: socket");
continue;
}
if (bind(rtex_rr_sockfd, p2->ai_addr, p2->ai_addrlen) == -1) {
close(rtex_rr_sockfd);
perror("listener: bind");
continue;
}
break;
}
if (p2 == NULL) {
fprintf(stderr, "listener: failed to bind socket\n");
return 2;
}
if((rrw = getaddrinfo(NULL, RTEX_R_PORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rrw));
return 1;
}
for(p3 = servinfo; p3 != NULL; p3 = p3->ai_next) {
if((rtex_rw_sockfd = socket(p3->ai_family, p3->ai_socktype,
p3->ai_protocol)) == -1) {
perror("server: socket");
continue;
}
break;
}
if (p3 == NULL) {
fprintf(stderr, "listener: failed to bind socket\n");
return 2;
}
//free up memory no longer needed after binding has completed
freeaddrinfo(servinfo);
FD_ZERO(&readfds);
FD_ZERO(&writefds);
FD_SET(rv, &readfds);
FD_SET(rrr, &readfds);
FD_SET(rrw, &writefds);
printf("Listen Mode\n");
//main while loop, listens for packets.
//Upon receipt of packet, information is stored in a struct for processing.
first=0;
while(1)
{
i=0;
inet_packet = EmptyPacket;
rt_empty=true;
tv.tv_sec = 50;
if(rv > rrr && rv > rrw)
max_fd = (rv + 1);
else if(rrr > rv && rrr > rrw)
max_fd = (rrr + 1);
else if(rrw > rv && rrw > rrr)
max_fd = (rrw + 1);
printf("before select...\n");
select(max_fd, &readfds, &writefds, NULL, NULL);
printf("after select...\n");
addr_len = sizeof their_addr;
if(FD_ISSET(rv, &readfds))
{
printf("rv is set...\n");
if((numbytes = recvfrom(sockfd, buf, sizeof(buf), 0,
(struct sockaddr *)&their_addr, &addr_len)) == -1) {
perror("recvfrom");
exit(1);
}
} else if(FD_ISSET(rrr, &readfds))
{
printf("rr read is set...\n");
if((numbytes = recvfrom(rtex_rr_sockfd, buf, sizeof(buf), 0,
(struct sockaddr *)&right_addr, &addr_len)) == -1) {
perror("recvfrom");
exit(1);
}
} else if(FD_ISSET(rrw, &writefds))
{
printf("rr write is set...\n");
if((numbytes = sendto(rtex_rw_sockfd, inet_packet.payload, sizeof(inet_packet.payload),
0, p3->ai_addr, p3->ai_addrlen)) == -1) {
perror("sendto rr");
exit(1);
}
}
運行程序,然后在終端啟動后按Enter。 它可能會從選擇中返回。 為什么? 因為您告訴選擇要聽的唯一東西是fd 0,所以stdin! rv
, rrr
和rrw
只是從getaddrinfo()
返回的值,而您只是忽略了socket()
返回的實際fd。 由於所有測試值彼此相等,因此max_fd
也將為垃圾值。 (如果碰巧為零,它甚至不會對標准輸入做出反應)
另外,下次,請將代碼簡化為最小示例 。 如果您的問題是選擇不返回,則例如。 所有處理代碼都是完全無關的,一個套接字就足夠了,而使用getaddrinfo()
則是多余的。 同樣,出於最小的示例,您在刪除getaddrinfo()
時可能會自己發現錯誤。
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