使用 c 的 TCP/IP 服务器

Question

我想制作一个服务器-客户端程序。我找不到的第一件事是让服务器永远不会关闭并接受每个客户端。我在服务器上放了一段时间 (1) 来运行，但在 3 个连接之后到一个客户端，我的服务器停止接受其他连接，我删除了这个。我找不到如何构建这个想法。另外我想创建 TCP/IP 套接字，所以我用正确的方式制作套接字吗？

我正在 Visual Studio Code 开发 ubuntu。

服务器：

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>  
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/socket.h> 
#include <sys/types.h>
#include <netinet/in.h> 
#define PORT 8080
int main(int argc,char* argv[]){

int server_fd, new_socket, valread; 
struct sockaddr_in address; 
int opt = 1; 
int addrlen = sizeof(address); 

char *hello = "Hello from server";

    while(1){
    char buffer[1024] = {0}; 
    printf("Server\n");
    // Creating socket file descriptor 
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) { 
        perror("socket failed"); 
        exit(EXIT_FAILURE); 
    } 

    // Forcefully attaching socket to the port 8080 
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT,&opt, 
    sizeof(opt))) { 
        perror("setsockopt"); 
        exit(EXIT_FAILURE); 
    } 
    address.sin_family = AF_INET; 
    address.sin_addr.s_addr = INADDR_ANY; 
    address.sin_port = htons( PORT ); 

    // Forcefully attaching socket to the port 8080 
    if (bind(server_fd, (struct sockaddr *)&address,sizeof(address))<0) { 
        perror("bind failed"); 
        exit(EXIT_FAILURE); 
    } 

    if (listen(server_fd, 1) < 0) { 
        perror("listen"); 
        exit(EXIT_FAILURE); 
    }
    printf("Listening...\n");
    if ((new_socket = accept(server_fd, (struct sockaddr *)&address,(socklen_t*)&addrlen))<0) { 
        perror("accept"); 
        exit(EXIT_FAILURE); 
    }

    valread = read( new_socket , buffer, 1024); 
    printf("%s\n",buffer ); 
    send(new_socket , hello , strlen(hello) , 0 ); 
    printf("Hello message sent\n"); 
}
return 0;
}

到目前为止我的客户：

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>  
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/socket.h> 
#include <sys/types.h>
#include <arpa/inet.h> 

#define PORT 8080

int main(int argc,char* argv[]){

char* command = (char*) malloc(15*sizeof(char));
int sock = 0, valread; 
struct sockaddr_in serv_addr; 
char *hello = "Hello from client"; 
char buffer[1024] = {0};

printf("Client\n");

if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0){ 
    printf("\n Socket creation error \n"); 
    return -1; 
} 

serv_addr.sin_family = AF_INET; 
serv_addr.sin_port = htons(PORT); 

// Convert IPv4 and IPv6 addresses from text to binary form 
if(inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr)<=0)  { 
    printf("\nInvalid address/ Address not supported \n"); 
    return -1; 
} 

if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) { 
    printf("\nConnection Failed \n"); 
    return -1; 
}


send(sock , hello , strlen(hello) , 0 ); 
printf("Hello message sent\n"); 
valread = read( sock , buffer, 1024); 
printf("%s\n",buffer ); 

return 0;
}

Answer 1

您必须只在接受客户端的代码周围放置循环。服务器套接字本身只创建一次。

// Creation of server socket(), bind(), listen()
while (1) {
   if ((new_socket = accept(server_fd, (struct sockaddr *)&address,
                                              (socklen_t*)&addrlen)) < 0) { 
       perror("accept"); 
       exit(EXIT_FAILURE); 
   }

   valread = read( new_socket , buffer, 1024); 
   printf("%s\n",buffer ); 
   send(new_socket , hello , strlen(hello) , 0 ); 
   printf("Hello message sent\n"); 
}

此外，您应该在通信完成后（即printf("Hello message sent\n");:

close(new_socket);

请注意，客户端是以这种方式连续服务的。它们可以同时连接，但一次只能为一个客户端提供服务。如果您需要并发处理，您可以例如fork() 多个进程，每个处理一个客户端，或者使用poll() 或select() 在一个线程中处理多个客户端。