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我需要使用單個服務器（作爲主服務器）和多個客戶端來調試多人遊戲的代碼。我想使用select和FD_Set函數將這些多個客戶端連接到服務器。爲什麼select（）不會在我的代碼中返回？
一旦客戶端連接到服務器，我將它們的文件描述符保存在一個數組中，並檢查數據是否可用於文件讀取（使用select）。如果是，請閱讀數據，否則我想向所有客戶端廣播消息。這是循環重複運行。每一秒，我都想向所有客戶播放一條消息。同時，我也想從客戶端接收數據。所以我在選擇函數的幫助下檢查數據的可用性。
這裏是我的代碼：
Server.c：
#include"stdio.h"
#include"stdlib.h"
#include"sys/types.h"
#include"sys/socket.h"
#include"string.h"
#include"netinet/in.h"
#include "sys/select.h"
#include <fcntl.h>
#define PORT 5000
#define BUF_SIZE 2000
#define CLADDR_LEN 100
int arr[4] = { 0 };
char clientAddr[4][CLADDR_LEN];
void main() {
struct sockaddr_in addr, cl_addr;
int sockfd, len, ret, newsockfd;
char buffer[BUF_SIZE];
fd_set fds;
int maxfd = -1;
int i = 0, j = 0;
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0) {
printf("Error creating socket!\n");
exit(1);
}
printf("Socket created...\n");
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = INADDR_ANY;
addr.sin_port = PORT;
ret = bind(sockfd, (struct sockaddr *) &addr, sizeof(addr));
if (ret < 0) {
printf("Error binding!\n");
exit(1);
}
printf("Binding done...\n");
printf("Waiting for a connection...\n");
listen(sockfd, 4);
for (j = 0; j < 2; j++) { //infinite loop
len = sizeof(cl_addr);
newsockfd = accept(sockfd, (struct sockaddr *) &cl_addr, &len);
if (newsockfd < 0) {
printf("Error accepting connection!\n");
exit(1);
}
printf("Connection accepted...\n");
inet_ntop(AF_INET, &(cl_addr.sin_addr), clientAddr[j], CLADDR_LEN);
arr[j] = newsockfd;
printf("\n%d", newsockfd);
//FD_ZERO(&fds);
//FD_SET(newsockfd, &fds);
}
close(sockfd);
for (j = 0; j < 2; j++) {
if (arr[j] > maxfd)
maxfd = arr[j];
// FD_SET(arr[j], &fds);
// fcntl(arr[i], F_SETFL, O_NONBLOCK); //stop listening for new connections by the main process.
} //the child will continue to listen.
//the main process now handles the connected client.
while (1) {
for (i = 0; i < 2; i++) {
FD_SET(arr[i], &fds);
}
int returned = select(maxfd + 1, &fds, NULL, NULL, NULL);
if (returned) {
for (i = 0; i < 2; i++) {
if (FD_ISSET(arr[2], &fds)) {
ret = recvfrom(arr[i], (void*) &buffer, sizeof(buffer), 0,
NULL, NULL);
if (ret < 0) {
printf("Error receiving data!\n");
exit(1);
}
printf("%s", buffer);
}
}
}
for (j = 0; j < 2; j++) {
ret = sendto(arr[j], "abc", BUF_SIZE, 0,
(struct sockaddr *) &cl_addr, len);
if (ret < 0) {
printf("Error sending data!\n");
exit(1);
}
printf("Sent data to %s: %s\n", clientAddr[j], buffer);
}
}
/*while (1) {
for (j = 0; j < 2; j++) {
memset(buffer, 0, BUF_SIZE);
if (FD_ISSET(arr[j], &fds)) {
ret = recvfrom(arr[j], buffer, BUF_SIZE, 0,
(struct sockaddr *) &cl_addr, &len);
if (ret < 0) {
printf("Error receiving data!\n");
exit(1);
}
printf("Received data from %s: %s\n", clientAddr[j], buffer);
}
}
for (j = 0; j < 2; j++) {
ret = sendto(arr[j], "abc", BUF_SIZE, 0,
(struct sockaddr *) &cl_addr, len);
if (ret < 0) {
printf("Error sending data!\n");
exit(1);
}
printf("Sent data to %s: %s\n", clientAddr[j], buffer);
}
/* close(arr[0]);
close[arr[1]);
close(arr[2]);
close(arr[3]);
}*/
}
client.c：
#include"stdio.h"
#include"stdlib.h"
#include"sys/types.h"
#include"sys/socket.h"
#include"string.h"
#include"netinet/in.h"
#include"netdb.h"
#define PORT 5555
#define BUF_SIZE 2000
int main(int argc, char**argv) {
struct sockaddr_in addr, cl_addr;
int sockfd, ret;
char buffer[BUF_SIZE];
struct hostent * server;
char * serverAddr;
if (argc < 2) {
printf("usage: client < ip address >\n");
exit(1);
}
serverAddr = argv[1];
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0) {
printf("Error creating socket!\n");
exit(1);
}
printf("Socket created...\n");
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr(serverAddr);
addr.sin_port = PORT;
ret = connect(sockfd, (struct sockaddr *) &addr, sizeof(addr));
if (ret < 0) {
printf("Error connecting to the server!\n");
exit(1);
}
printf("Connected to the server...\n");
memset(buffer, 0, BUF_SIZE);
//printf("Enter your message(s): ");
//while (fgets(buffer, BUF_SIZE, stdin) != NULL) {
sleep(10);
ret = sendto(sockfd, "a", BUF_SIZE, 0, (struct sockaddr *) &addr, sizeof(addr));
if (ret < 0) {
printf("Error sending data!\n\t-%s", buffer);
}
ret = recvfrom(sockfd, buffer, BUF_SIZE, 0, NULL, NULL);
if (ret < 0) {
printf("Error receiving data!\n");
} else {
printf("Received: ");
fputs(buffer, stdout);
printf("\n");
}
return 0;
}
（客戶端傳遞了一個IP地址）
This does 不行。在調試服務器時，它在選擇時等待並且沒有收到或發送任何內容。問題可能是什麼？
你似乎檢查'if（FD_ISSET（arr [2]'，但你從未在'arr [2]'中描述符上調用過FD_SET（），並且忘記檢查arr [0]上的FD_ISSET（）和arr [1 ] – nos 2014-11-06 12:57:45