udp服务器使用connect()函数指明套接字的目的地址/端口号，使服务器只接受特定主机的请求；
udp服务器调用了bind()函数为服务器套接字绑定本地地址/端口，使得客户端知道发数据的目的地址/端口；
udp客户端调用connect()函数指明目的地址/端口后，可使用send()函数向目的地址发送数据；
udp客户端在发送数据之前， 用bind()函数绑定本地地址/端口， 可避免操作系统该套接字随机分配地址信息和端口号；
上代码
配置参数
#define INET_SERVER_IP_ADDR "192.168.1.39"
#define INET_CLIENT_IP_ADDR "192.168.1.102"
#define SERVER_UDP_PORT "9877"
#define CLIENT_UDP_PORT "9871"
#define INET_IP_ADDR_LENGTH (16U)
#define UDP_DGRAM_LEN_MAX (1024U)
#define MSG_SEND_INTERVAL (50000) /* unit: us */服务器：
void server_init(void)
{
pid_t pid;
siginfo_t info;
int server_sockfd;
struct sockaddr_in local_addr, remote_addr;
/* print_addrinfo("ftp"); */ /* domain daytime stream http ftp */
/*____________________________________________________________________________________________*/
server_sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(server_sockfd < 0)
{
perror("socket() fail");
exit(EXIT_FAILURE);
}
/* socket_set_reuseaddr(); */
/*____________________________________________________________________________________________*/
memset(&local_addr, 0, sizeof(local_addr));
if(inet_pton(AF_INET, INET_SERVER_IP_ADDR, &(local_addr.sin_addr)) < 0)
{
perror("inet_pton() error");
close(server_sockfd);
exit(EXIT_FAILURE);
}
else
{
local_addr.sin_family = AF_INET;
local_addr.sin_port = htons(atol(SERVER_UDP_PORT));
}
if(-1 == bind(server_sockfd, (struct sockaddr *)(&local_addr), sizeof(local_addr)))
{
perror("bind() fail");
close(server_sockfd);
exit(EXIT_FAILURE);
}
/*____________________________________________________________________________________________*/
char client_addr[INET_IP_ADDR_LENGTH];
int ret;
char rcv_buf[UDP_DGRAM_LEN_MAX] = {'\0'};
memset(&remote_addr, 0, sizeof(remote_addr));
socklen_t addr_len = sizeof(remote_addr);
ret = recvfrom(server_sockfd, rcv_buf, UDP_DGRAM_LEN_MAX, 0, (struct sockaddr *)&remote_addr, &addr_len);
if(-1 == ret)
{
perror("recvfrom() failure");
exit(EXIT_FAILURE);
}
else
{
if(NULL == inet_ntop(AF_INET, &remote_addr.sin_addr, client_addr, INET_IP_ADDR_LENGTH))
{
perror("inet_ntop() error");
}
else
{
printf("Received %d Bytes From Client: %s (Port: %u)\n", ret, client_addr, ntohs(remote_addr.sin_port));
printf("%s\n", rcv_buf);
}
}
/*____________________________________________________________________________________________*/
#if false
if(inet_pton(AF_INET, INET_CLIENT_IP_ADDR, &(remote_addr.sin_addr)) < 0)
{
perror("inet_pton() error");
exit(EXIT_FAILURE);
}
else
{
remote_addr.sin_family = AF_INET;
remote_addr.sin_port = htons(atol(CLIENT_UDP_PORT));
}
#endif
#ifdef SERVER_CONNECT_EN
if(-1 == connect(server_sockfd, (struct sockaddr *)(&remote_addr), sizeof(remote_addr)))
{
perror("connect() fail");
close(server_sockfd);
exit(EXIT_FAILURE);
}
else
{
printf("Successfully Connected To Client-Socket!\n");
}
/*____________________________________________________________________________________________*/
char send_buf[] = {"Of course, I still love you!"};
if(-1 == send(server_sockfd, send_buf, sizeof(send_buf), 0))
{
perror("send() fail");
}
#else
char send_buf[] = {"Of course, I still love you!"};
if(-1 == sendto(server_sockfd, send_buf, sizeof(send_buf), 0, (struct sockaddr *)(&remote_addr), sizeof(remote_addr)))
{
perror("sendto() fail");
}
#endif
/*____________________________________________________________________________________________*/
sigaction_config();
/*____________________________________________________________________________________________*/
pid = fork();
if(pid < 0)
{
perror("fork() error");
}
else if(pid == 0) /* child */
{
#ifdef SERVER_CONNECT_EN
dgram_send(server_sockfd);
#else
dgram_sendto(server_sockfd, (struct sockaddr *)(&remote_addr), sizeof(remote_addr));
#endif
}
else /* parent */
{
#ifdef SERVER_CONNECT_EN
dgram_recv(server_sockfd);
#else
dgram_receive(server_sockfd);
#endif
if(-1 == waitid(P_PID, 0, &info, WEXITED))
{
perror("waitid() failure");
}
close(server_sockfd);
exit(EXIT_SUCCESS);
}
}客户端：
void client_init(void)
{
pid_t pid;
siginfo_t info;
int client_sockfd;
struct sockaddr_in local_addr, remote_addr;
/*____________________________________________________________________________________________*/
client_sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(client_sockfd < 0)
{
perror("socket() fail");
exit(EXIT_FAILURE);
}
/*____________________________________________________________________________________________*/
memset(&local_addr, 0, sizeof(local_addr));
local_addr.sin_family = AF_INET;
local_addr.sin_port = htons(atol(CLIENT_UDP_PORT));
local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
if(-1 == bind(client_sockfd, (struct sockaddr *)(&local_addr), sizeof(local_addr)))
{
perror("bind() fail");
close(client_sockfd);
exit(EXIT_FAILURE);
}
/*____________________________________________________________________________________________*/
memset(&remote_addr, 0, sizeof(remote_addr));
if(inet_pton(AF_INET, INET_SERVER_IP_ADDR, &(remote_addr.sin_addr)) < 0)
{
perror("inet_pton() error");
close(client_sockfd);
exit(EXIT_FAILURE);
}
else
{
remote_addr.sin_family = AF_INET;
remote_addr.sin_port = htons(atol(SERVER_UDP_PORT));
}
/*____________________________________________________________________________________________*/
char send_buf[] = {"Hello World!"};
int ret;
ret = sendto(client_sockfd, send_buf, sizeof(send_buf), 0, (struct sockaddr *)(&remote_addr), sizeof(remote_addr));
if(-1 == ret)
{
perror("sendto() failure");
close(client_sockfd);
exit(EXIT_FAILURE);
}
else
{
printf("Say \"Hello\" To Server: %s With Port: %s\n", INET_SERVER_IP_ADDR, SERVER_UDP_PORT);
fflush(stdout);
}
/*____________________________________________________________________________________________*/
char server_addr[INET_IP_ADDR_LENGTH];
char rcv_buf[UDP_DGRAM_LEN_MAX] = {'\0'};
memset(&remote_addr, 0, sizeof(remote_addr));
socklen_t addr_len = sizeof(remote_addr);
ret = recvfrom(client_sockfd, rcv_buf, UDP_DGRAM_LEN_MAX, 0, (struct sockaddr *)&remote_addr, &addr_len);
if(-1 == ret)
{
perror("recvfrom() failure");
exit(EXIT_FAILURE);
}
else
{
if(NULL == inet_ntop(AF_INET, &remote_addr.sin_addr, server_addr, INET_IP_ADDR_LENGTH))
{
perror("inet_ntop() error");
}
else
{
printf("Received %d Bytes From Server: %s (Port: %u)\n", ret, server_addr, ntohs(remote_addr.sin_port));
printf("%s\n", rcv_buf);
}
}
/*____________________________________________________________________________________________*/
if(-1 == connect(client_sockfd, (struct sockaddr *)(&remote_addr), sizeof(remote_addr)))
{
perror("connect() fail");
close(client_sockfd);
exit(EXIT_FAILURE);
}
else
{
printf("Successfully Connected To Server-Socket!\n");
}
/*____________________________________________________________________________________________*/
sigaction_config();
/*____________________________________________________________________________________________*/
pid = fork();
if(pid < 0)
{
perror("fork() error");
}
else if(pid == 0) /* child */
{
dgram_send(client_sockfd);
}
else /* parent */
{
dgram_recv(client_sockfd);
if(-1 == waitid(P_PID, 0, &info, WEXITED))
{
perror("waitid() failure");
}
close(client_sockfd);
exit(EXIT_SUCCESS);
}
}测试：
服务端：
客户端：
参考链接：
https://blog.csdn.net/wanggao_1990/article/details/108020190
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