C语言 socket编程实例

一. 面向连接的流式套接字 C/S 例子

在树莓派下，新建一个 Server1.c，命令 nano Server1.c，然后写入如下内容

#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#define PORT "9090" // the port users will be connecting to 
#define BACKLOG 10 
// how many pending connections queue will hold 
void sigchld_handler(int s) 
{
    
	while(waitpid(-1, NULL, WNOHANG) > 0); 
}
// get sockaddr, IPv4 or IPv6: 
void *get_in_addr(struct sockaddr *sa) 
{
    
    if (sa->sa_family == AF_INET) {
    
    	return &(((struct sockaddr_in*)sa)->sin_addr); 
    }
	return &(((struct sockaddr_in6*)sa)->sin6_addr); 
}
int main(void) 
{
    
    int sockfd, new_fd; // listen on sock_fd, new connection on new_fd 
    struct addrinfo hints, *servinfo, *p; 
    struct sockaddr_storage their_addr; // connector's address information 
    socklen_t sin_size; 
    struct sigaction sa; 
    int yes=1;
    char s[INET6_ADDRSTRLEN]; 
    int rv; 
    memset(&hints, 0, sizeof hints); 
    hints.ai_family = AF_UNSPEC; 
    hints.ai_socktype = SOCK_STREAM; 
    hints.ai_flags = AI_PASSIVE; // use my IP 
    if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
    
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); 
        return 1; 
	}
// loop through all the results and bind to the first we can 
    for(p = servinfo; p != NULL; p = p->ai_next) {
    
    if ((sockfd = socket(p->ai_family, p->ai_socktype, 
    p->ai_protocol)) == -1) {
    
        perror("server: socket"); 
        continue; 
    }
    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, 
    sizeof(int)) == -1) {
    
        perror("setsockopt"); 
        exit(1); 
    }
    if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
    
        close(sockfd); 
        perror("server: bind"); 
        continue; 
    }
    break; 
}
    if (p == NULL) {
    
        fprintf(stderr, "server: failed to bind\n"); 
        return 2; 
    }
    freeaddrinfo(servinfo); // all done with this structure 
    if (listen(sockfd, BACKLOG) == -1) {
    
        perror("listen"); 
        exit(1); 
    }
    sa.sa_handler = sigchld_handler; // reap all dead processes 
    sigemptyset(&sa.sa_mask); 
    sa.sa_flags = SA_RESTART; 
    if (sigaction(SIGCHLD, &sa, NULL) == -1) {
    
        perror("sigaction"); 
        exit(1); 
    }
    printf("server: waiting for connections...\n"); 
    while(1) {
    // main accept() loop 
        sin_size = sizeof their_addr; 
        new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size); 
        if (new_fd == -1) {
    
            perror("accept"); 
            continue; 
        }
        inet_ntop(their_addr.ss_family, 
        get_in_addr((struct sockaddr *)&their_addr), 
        s, sizeof s); 
        printf("server: got connection from %s\n", s); 
        if (!fork()) {
    // this is the child process 
            close(sockfd); // child doesn't need the listener 
            if (send(new_fd, "Hello, world!", 13, 0) == -1) 
            perror("send"); 
            close(new_fd); 
            exit(0); 
        }
        close(new_fd); // parent doesn't need this 
    }
    return 0; 
}

然后编译并运行

gcc Server1.c -o Server1
./Server1

在Ubuntu系统下，新建一个Client1.c文件，命令gedit Client1.c，然后写入如下内容

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define PORT "9090"  //the port client will be connecting to
#define MAXDATASIZE 100  //max number of bytes we can get at once

//get sockaddr, IPv4 or IPv6
void *get_in_addr(struct sockaddr *sa)
{
   
	if(sa->sa_family == AF_INET)
	{
   
		return &(((struct sockaddr_in*)sa)->sin_addr);
	}
	return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(int argc, char *argv[])
{
   
	int sockfd, numbytes;
	char buf[MAXDATASIZE];
	struct addrinfo hints, *servinfo, *p;
	int rv;
	char s[INET6_ADDRSTRLEN];
	if(argc != 2)
	{
   
		fprintf(stderr, "usage:client hostname\n");
		exit(1);
	}
	memset(&hints, 0, sizeof hints);
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	if((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0)
	{
   
		fprintf(stderr, "getaddrinfo:%s\n",gai_strerror(rv));
		return 1;
	}
    // loop through all the results and connect to the first we can 
	for(p = servinfo; p != NULL; p = p->ai_next)
	{
   
		if((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1)
		{
   
			perror("client:socket");
			continue;
		}
		if(connect(sockfd, p->ai_addr, p->ai_addrlen) == -1)
		{
   
			close(sockfd);
			perror("client:connect");
			continue;
		}
		break;
	}
	if(p == NULL)
	{
   
		fprintf(stderr, "client:failed to connect\n");
		return 2;
	}
	inet_ntop(p->ai_family, get_in_addr((struct sockaddr*)p->ai_addr), s, sizeof s);
	printf("client:connecting to %s\n",s);
	freeaddrinfo(servinfo);// all done with this structure 
	if((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1)
	{
   
		perror("recv");
		exit(1);
	}
	buf[numbytes] = '\0';
	printf("client:received %s\n",buf);
	close(sockfd);
	return 0;
}

gcc Client1.c -o Client1
./Client1 192.168.43.161
# 二级目录

二. 非阻塞的多人聊天服务器端例子

在树莓派下，新建一个Server2.c文件，命令nano Server2.c，然后写入如下内容

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define PORT "9090"  //port we're listening on

//get sockaddr,IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
   
    if(sa->sa_family == AF_INET){