UDP编程相比TCP来说相对简单主要用到sendto()和recvfrom()这两个函数,接下来主要介绍一下这两个函数。
头文件
#include <sys/types.h>
#include <sys/socket.h>
函数原型
int sendto (int s, const void *buf, int len, unsigned int flags, const struct sockaddr *to, int tolen);
int recvfrom(int s, void *buf, int len, unsigned int flags, struct sockaddr *from, int *fromlen);
函数说明
sendto(),是把UDP数据报发给指定地址;
recvfrom()是从指定地址接收UDP数据报。
参数说明
s: socket描述符。
buf: UDP数据报缓存地址。
len: UDP数据报长度。
flags: 该参数一般为0。
to: sendto()函数参数,struct sockaddr_in类型,指明UDP数据发往哪里报。
tolen: 对方地址长度,一般为:sizeof(struct sockaddr_in)。
fromlen:recvfrom()函数参数,struct sockaddr_in类型,指明从哪里接收UDP数据报。
函数返回值
对于sendto()函数,成功则返回实际传送出去的字符数,失败返回-1,错误原因存于errno 中。
对于recvfrom()函数,成功则返回接收到的字符数,失败则返回-1,错误原因存于errno中。
关于UDP数据报
UDP都是以数据报的形式进行发送和接收的,而TCP是以数据流的形式进行发送和接收的。数据报和数据流,这两者要区分开来。
UDP Server和Client源码实例
UDP Server:
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <getopt.h>
#include <errno.h>
void print_usage(char *progname)
{
printf("%s usage: \n", progname);
printf("-p(--port): sepcify server listen port.\n");
printf("-h(--Help): print this help information.\n");
return ;
}
int main(int argc,char **argv)
{
int ch = 0;
int port = 0;
int rv = -1;
int len = -1;
int servfd = 0;
int addr_len = sizeof(struct sockaddr_in);
char buf[256];
struct sockaddr_in servaddr;
struct option opts[] = {
{"port", required_argument, NULL, 'p'},
{"help", no_argument, NULL, 'h'},
{NULL, 0, NULL, 0}
};
while( (ch=getopt_long(argc, argv, "p:h", opts, NULL)) != -1 )
{
switch(ch)
{
case 'p':
port=atoi(optarg);
break;
case 'h':
print_usage(argv[0]);
return 0;
}
}
if( !port )
{
print_usage(argv[0]);
return 0;
}
servfd = socket(AF_INET,SOCK_DGRAM,0);
if(servfd < 0)
{
printf("create servfd failure:%s\n",strerror(errno));
return -1;
}
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(port);
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
if( bind(servfd,(struct sockaddr *)&servaddr,sizeof(servaddr)) < 0)
{
printf("bind servfd[%d] failure:%s\n",servfd,strerror(errno));
return -2;
}
printf("bind servfd[%d] successfully!\n",servfd);
while(1)
{
memset(buf,0,sizeof(buf));
len = recvfrom(servfd,buf,sizeof(buf),0,(struct sockaddr *)&servaddr,&addr_len);
if(rv < -1)
{
printf("recvfrom data failure\n",strerror(errno));
continue;
}
printf("Received a string from client %s, string is: %s\n",inet_ntoa(servaddr.sin_addr), buf);
rv = sendto(servfd,buf,len,0,(struct sockaddr *)&servaddr,sizeof(servaddr));
if(rv < 0)
{
printf("reply data failure %s\n",strerror(errno));
continue;
}
printf("reply data sucessfully!\n");
}
}
UDP Client:
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <getopt.h>
#include <errno.h>
void print_usage(char *progname)
{
printf("%s usage: \n", progname);
printf("-i(--ipaddr): sepcify server IP address\n");
printf("-p(--port): sepcify server port.\n");
printf("-h(--Help): print this help information.\n");
return ;
}
int main(int argc,char **argv)
{
int sockfd = 0;
int ch = 0;
int port = 0;
int len = 0;
int rv = -1;
int addr_len = sizeof(struct sockaddr_in);
char buf[1024]={0};
char *servip;
struct sockaddr_in sockaddr;
struct option opts[] = {
{"ipaddr", required_argument, NULL, 'i'},
{"port", required_argument, NULL, 'p'},
{"help", no_argument, NULL, 'h'},
{NULL, 0, NULL, 0}
};
while( (ch=getopt_long(argc, argv, "i:p:h", opts, NULL)) != -1 )
{
switch(ch)
{
case 'i':
servip=optarg;
break;
case 'p':
port=atoi(optarg);
break;
case 'h':
print_usage(argv[0]);
return 0;
}
}
if( !servip || !port )
{
print_usage(argv[0]);
return 0;
}
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if(sockfd < 0)
{
printf("create sockfd failure:%s\n",strerror(errno));
return -1;
}
sockaddr.sin_family = AF_INET;
sockaddr.sin_port = htons(port);
inet_aton(servip,&sockaddr.sin_addr);
while(1)
{
printf("please enter a set of strings:\n");
len = read(STDIN_FILENO,buf,sizeof(buf));
if(len < 0)
{
printf("read data failure!\n");
continue;
}
rv = sendto(sockfd,buf,len,0,(struct sockaddr *)&sockaddr,sizeof(sockaddr));
if(rv < 0)
{
printf("send data failre:%s\n",strerror(errno));
break;
}
printf("send data[%d] successfully!\n",rv);
len = recvfrom(sockfd,buf,sizeof(buf),0,(struct sockaddr *)&sockaddr,&addr_len);
if( len < 0)
{
printf("recover data[%d] failure:%s \n",len,strerror(errno));
continue;
}
printf("Receive from server: %s\n", buf);
}
参考博客:http://velep.com/archives/934.html
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