我需要帮助调试具有单个服务器（充当主服务器）和多个客户端的多人游戏的一些代码。我想使用 select 和 FD_Set 函数将多个客户端连接到服务器。
一旦客户端连接到服务器，我将它们的文件描述符保存在一个数组中，并检查文件上是否有数据可供读取（使用 select）。如果是，则读取数据，否则我想向所有客户端广播一条消息。这是在循环中重复运行的。每一秒，我都想向所有客户广播一条消息。同时，我也想从客户端接收数据。所以我正在借助 select 函数检查数据的可用性。
这是我的代码：
服务器.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;
}
（向客户端传递一个 IP 地址。）
这是行不通的。调试服务器时，它在 select 处等待，但没有接收或发送任何内容。可能是什么问题？
可能是因为您没有监听正确的端口。
sockaddr_inmemset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(PORT);
上面是 select 工作原理的示例，在 while 循环中，您必须设置 timeval 结构和套接字 sd
while (1) {
FD_ZERO(&readfds);
FD_SET(sd, &readfds);
tv.tv_sec = 0;
tv.tv_usec = 0;
rv = select(sd + 1, &readfds, NULL, NULL, &tv);
if (rv == 1) {
/*recvfrom*/
}
}
安全第一
FD_ZERO(&readfds)FDSETclientfds如果您检查客户端并且客户端发送数据成功，请检查此行
for (i = 0; i < 2; i++) {
if (FD_ISSET(arr[2], &fds)) {
ret = recvfrom(arr[i], (void*) &buffer, sizeof(buffer), 0,
NULL, NULL);
在你的代码中
FD_ISSET(arr[2], &fds)FD_ISSET(arr[i], &fds)
因为如果你不能改变
arr[i]