使用 c 的 TCP/IP 服务器

Question

我想做一个服务器-客户端程序。我找不到的第一件事是使服务器永不关闭并接受每个客户端。我在服务器上放了一个 while(1( 来运行，但是在与一个客户端连接 3 次后，我的服务器停止接受其他连接，我删除了这个连接。我找不到如何建立这种想法。我也想创建TCP/IP套接字，所以我是否以正确的方式制作套接字？

我在Visual Studio Code上工作。

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("Servern");
// 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("%sn",buffer ); 
send(new_socket , hello , strlen(hello) , 0 ); 
printf("Hello message sentn"); 
}
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("Clientn");
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 sentn"); 
valread = read( sock , buffer, 1024); 
printf("%sn",buffer ); 
return 0;
}

Answer 1

您必须仅将循环放在接受客户端的代码周围。服务器套接字本身仅创建一次。

// 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("%sn",buffer ); 
send(new_socket , hello , strlen(hello) , 0 ); 
printf("Hello message sentn"); 
}

此外，您应该在通信完成后(即在printf("Hello message sentn");之后(在 while 块结束时关闭客户端套接字：

close(new_socket);

请注意，客户端以这种方式串行服务。它们可以并发连接，但一次只能为一个客户端提供服务。如果需要并发处理，例如，可以fork()多个进程，每个进程处理一个客户端，或者使用poll()或select()在一个线程中处理多个客户端。