Complete TCP forwarding server (kernel linked list + mutex)

// The following code is for reference only , If there are any mistakes, please comment and correct , thank you ！

// Server side
server.c

#include "myhead.h" // All required header files （ Except for the kernel linked list ）
#include "kernel_list.h"// Kernel linked list header file 

// Define a mutex 
pthread_mutex_t m;

// Design client nodes 
struct client
{
    
	char ip[50];	// Save client ip
	unsigned int port;	// Save the client port 
	int connfd;	// Save client connection socket 
	
	struct list_head list;	// Define the kernel linked list 
};

// Chain header node 
struct client *head = NULL;

// Initializing the header node 
struct client *list_init(void)
{
    
	struct client *head = calloc(1, sizeof(struct client));
	if(head == NULL)
	{
    
		perror("calloc failed");
		exit(0);
	}
	INIT_LIST_HEAD(&head->list);	
}

// single shot ( To the designated person )
bool send_single(char *msg, unsigned short port)
{
    
	struct list_head *pos = NULL;
	struct client *tmp = NULL;
	
	// Lock shared resources 
	pthread_mutex_lock(&m);
	list_for_each(pos, &head->list)
	{
    
		// find pos The first address of the structure type of the linked list node ,list yes struct client Structure member of type 
		tmp =list_entry(pos, struct client, list);
		if(tmp->port == port)
		{
    
			write(tmp->connfd, msg, strlen(msg));
			pthread_mutex_unlock(&m);	// Abnormal situation , Unlock first , Quit again 
			return true;
		}
	}
	pthread_mutex_unlock(&m);	// The normal exit , Unlock 
	return false;
}

// Mass hair 
void send_broadcast(char *msg, struct client* new)
{
    
	struct list_head *pos = NULL;
	struct client *tmp = NULL;
	// Lock shared resources 
	pthread_mutex_lock(&m);
	list_for_each(pos, &head->list)// Traverse the linked list from scratch （ During traversal , Nodes cannot be deleted ）
	{
    
		tmp =list_entry(pos, struct client, list);
		if(tmp->port != new->port)
		{
    
			write(tmp->connfd, msg, strlen(msg));		
		}
	}
	pthread_mutex_unlock(&m); // Unlock shared resources 
}

// Client data receiving routine  
void *recvclient(void *arg)
{
    
	struct client *new = (struct client *)arg;
	char msg[100];
	char *str = NULL;
	//  Receive client data 
	while(1)
	{
    
		bzero(msg, 100);
		read(new->connfd, msg, sizeof(msg));
		printf(" come from [%s : %u] Customer service information : %s\n",  new->ip, new->port,msg);
		if(strncmp(msg, "quit", 4) == 0)// Client offline 
		{
    
			printf("[%s : %u] The client is offline \n", new->ip, new->port);
			close(new->connfd);	// Close socket 
			list_del(&new->list);	// Delete node from linked list 
			free(new);	// Free up the requested space 
			break;
		}
		else if((str = strstr(msg, ":")))	// single shot  // strstr:( Find the specified string in a string )
		{
    
			unsigned short port = atoi(msg);
			if(!send_single(str+1, port))
			{
    
				printf(" This port was not found \n");
			}
		}
		else	// Mass hair 
		{
    
			send_broadcast(msg, new);
		}	
	}
	pthread_exit(NULL);
}

int main(int argc, char *argv[])
{
    
	if(argc != 2)
	{
    
		printf("usage: %s <PORT>\n", argv[0]);
		exit(0);
	}
	
	// Initialize mutex 
	pthread_mutex_init(&m, NULL);
	
	int sockfd = socket(AF_INET, SOCK_STREAM, 0);//TCP
	if(sockfd == -1)
	{
    
		perror("sockfd faield");
		exit(0);
	}
	
	struct sockaddr_in saddr, caddr;
	bzero(&saddr, sizeof(saddr));
	bzero(&caddr, sizeof(caddr));
	saddr.sin_family = AF_INET;	//Ipv4
	saddr.sin_port = htons(atoi(argv[1]));
	saddr.sin_addr.s_addr = htonl(INADDR_ANY);//  Automatic access to IP
	if(bind(sockfd, (struct sockaddr*)&saddr, sizeof(saddr)) == -1)
	{
    
		perror("bind faield");
		exit(0);
	}
	// printf(" Binding success \n");
	
	if(listen(sockfd, 5) == -1)
	{
    
		perror("listen faield");
		exit(0);
	}
	printf(" Waiting for the connection \n");

	// Initialize chain header 
	head = list_init();    //head After defining the structure, we define 
	
	socklen_t addrlen = (socklen_t)sizeof(caddr);  //int len = sizeof(caddr);
	int connfd;
	// Waiting for multiple client connections 
	while(1)
	{
    
		if((connfd = accept(sockfd, (struct sockaddr*)&caddr, &addrlen)) == -1)
		{
    
			perror("accept faield");
			exit(0);
		}
		printf("[%s : %u] Successful connection \n", inet_ntoa(caddr.sin_addr), ntohs(caddr.sin_port));
		
		struct client *new = calloc(sizeof(struct client),1);  // Apply for new node space  
		if(new == NULL)
		{
    
			perror("calloc  Create nodes  failed");
			exit(0);
		}
		strcpy(new->ip, inet_ntoa(caddr.sin_addr));
		new->port = ntohs(caddr.sin_port);
		new->connfd = connfd;
		
		// Managing shared resources —— Client linked list 
		pthread_mutex_lock(&m);    // Lock 
		list_add_tail(&new->list, &head->list);	// Insert the end of the list 
		pthread_mutex_unlock(&m);  // Unlock 
		
		// Create thread , Receive client data 
		pthread_t tid;
		pthread_create(&tid, NULL, recvclient, new);
	}
	return 0;
}

// The end of the service
client.c

#include "myhead.h"

// receive messages 
void *Recv(void *arg)
{
    
	int sockfd = *(int *)arg;
	char msg[100];
	while(1)
	{
    
		bzero(msg, 100);
		read(sockfd, msg, 100);
		printf("%s\n", msg);
	}
	pthread_exit(NULL);
}


int main(int argc, char *argv[])
{
    
	if(argc != 3)
	{
    
		printf("usage: %s <IP> <PORT>\n", argv[0]);
		exit(0);
	}
	
	// Create a socket 
	int sockfd = socket(AF_INET, SOCK_STREAM, 0);
	if(sockfd == -1)
	{
    
		perror("sockfd faield");
		exit(0);
	}
	
	struct sockaddr_in saddr, caddr;
	bzero(&saddr, sizeof(saddr));
	bzero(&caddr, sizeof(caddr));
	saddr.sin_family = AF_INET;	//Ipv4
	saddr.sin_port = htons(atoi(argv[2]));
	// saddr.sin_addr.s_addr = htonl(INADDR_ANY);//  Automatic access to IP
	inet_pton(AF_INET, argv[1], &saddr.sin_addr);
	
	connect(sockfd, (struct sockaddr*)&saddr, sizeof(saddr));
	printf(" Successfully connected to the server \n");
	
	pthread_t tid;
	pthread_create(&tid, NULL, Recv, &sockfd);
	
	// Send message buffer 
	char msg[100] = {
    0};
	while(1)
	{
    
		bzero(msg, 100);
		printf(" Please enter the message to send ：\n");fflush(NULL);
		fgets(msg, 100, stdin);
		write(sockfd, msg, strlen(msg));
		if(strncmp(msg, "quit", 4) == 0)
		{
    
			printf(" sign out \n");
			break;
		}
	}	
	close(sockfd);
	return 0;
}

** Be careful ：** Connection required during compilation -lpthread