Linux UDP服务器编程
UDP主要使用sendto()
和recvfrom()
recvfrom()
函数原型如下:
#include <sys/types.h>
#include <sys/socket.h>
ssize_t recv(int sockfd, void *buf, size_t len, int flags);
ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *addrlen);
if (recvfrom(sockfd_s, buf, BUFFERSIZE, 0, (struct sockaddr*)&client_addr, &addrlen) == -1) {
perror("recvfrom");
continue; //UDP无连接传输,偶尔传输失败一次继续执行
}
特别注意:
- sockfd是本地套接字的描述符,在服务器端,就是服务器套接字;在客户端,就是客户端套接字
- buf是接受数据的缓冲区,len是缓冲区的大小
- flags一般为0
- 后面两个参数是用来获取:数据发送端的IP地址和端口号
sendto()
函数原型如下:
#include <sys/types.h>
#include <sys/socket.h>
ssize_t send(int sockfd, const void *buf, size_t len, int flags);
ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen);
if (sendto(sockfd_c, buf, strlen(buf)+1, 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
perror("sendto");
continue;
}
特别注意:
- sockfd是本地套接字的描述符,在发送的时候一般要绑定本地套接字与众所周知的IP地址和端口
- 参数中的套接字地址就是要发送的目的
示例
server.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <signal.h>
#include <errno.h>
#include <pthread.h>
#define SERVER_IP "172.17.44.154"
#define SERVER_PORT 5002
#define BUFFERSIZE 100
int main(int argc, const char *argv[])
{
int sockfd_s;
struct sockaddr_in server_addr, client_addr;
char buf[BUFFERSIZE];
socklen_t addrlen;
/* 创建套接字 */
if ((sockfd_s = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(-1);
}
/* 绑定服务器套接字 */
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_port = htons(SERVER_PORT);
server_addr.sin_family = AF_INET;
if (inet_pton(AF_INET, SERVER_IP, (void*)&server_addr.sin_addr.s_addr) != 1) {
perror("inet_pton");
exit(-1);
}
if (bind(sockfd_s, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
perror("bind");
exit(-1);
}
while (1) {
bzero(buf, BUFFERSIZE);
if (recvfrom(sockfd_s, buf, BUFFERSIZE, 0, (struct sockaddr*)&client_addr, &addrlen) == -1) {
perror("recvfrom");
continue; //UDP无连接传输,偶尔传输失败一次继续执行
} else { //成功收到
if (strcmp(buf, "quit") == 0) {
printf("the client %s/%d is quit\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
exit(0);
}
printf("recv from %s/%d data:%s\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), buf);
sendto(sockfd_s, buf, strlen(buf)+1, 0, (struct sockaddr*)&client_addr, (socklen_t)sizeof(client_addr)); //retroreflection
}
}
return 0;
}
client.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <signal.h>
#include <errno.h>
#include <pthread.h>
#define SERVER_IP "172.17.44.154"
#define SERVER_PORT 5002
#define BUFFERSIZE 100
int main(int argc, const char *argv[])
{
int sockfd_c;
struct sockaddr_in server_addr;
char buf[BUFFERSIZE]; //512
socklen_t addrlen;
/* 创建套接字 */
if ((sockfd_c = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(-1);
}
bzero(&server_addr, sizeof(server_addr));
server_addr.sin_port = htons(SERVER_PORT);
server_addr.sin_family = AF_INET;
if (-1 == inet_pton(AF_INET, SERVER_IP, (void*)&server_addr.sin_addr.s_addr)) {
perror("inet_pton");
exit(-1);
}
while (1) {
bzero(buf, BUFFERSIZE);
printf("input:");
fgets(buf, BUFFERSIZE-1, stdin);
if (sendto(sockfd_c, buf, strlen(buf)+1, 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
perror("sendto");
continue;
}
if (strcmp(buf, "quit\n") == 0) {
printf("the client will quit\n");
exit(0);
}
bzero(buf, BUFFERSIZE);
// bzero(&server_addr, sizeof(server_addr));
if (-1 == recvfrom(sockfd_c, buf, BUFFERSIZE - 1, 0, (struct sockaddr*)&server_addr, &addrlen)) {
perror("recvfrom");
continue;
}
else {
printf("recv from %s/%d data:%s\n", inet_ntoa(server_addr.sin_addr), ntohs(server_addr.sin_port), buf);
}
}
return 0;
}