我有以下服务器代码
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <string.h>
#include <stdio.h>
#define HELLO_PORT 12345
#define HELLO_GROUP "255.0.0.37"
main(int argc, char *argv[])
{
struct sockaddr_in addr;
struct sockaddr_in client,server;
int s,n;
char index;
int f;
char b1[100];
int fd, cnt,i=0;;
struct ip_mreq mreq;
//char *message="Hello, World!";
char *message=NULL;
/* create what looks like an ordinary UDP socket */
if ((fd=socket(AF_INET,SOCK_DGRAM,0)) < 0)
{
perror("socket");
exit(1);
}
s=socket(AF_INET,SOCK_DGRAM,0);
server.sin_family=AF_INET;
server.sin_port=2000;
server.sin_addr.s_addr=inet_addr("10.42.0.47");
bind(s,(struct sockaddr *)&server,sizeof(server));
printf("\nServer ready,waiting for client....\n");
n=sizeof(client);
/* set up destination address */
memset(&addr,0,sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_addr.s_addr=inet_addr(HELLO_GROUP);
addr.sin_port=htons(HELLO_PORT);
/* now just sendto() our destination! */
while (1)
{
recvfrom(s,b1,sizeof(b1),0,(struct sockaddr *) &client,&n);
printf("client : %s\n",b1);
//sleep(5);
index=b1[0];
f=b1[0];
//printf("b1[1] is %c\n",index);
//printf("b1[0] is %c\n",f);
f=32;
b1[0]=f;
//printf("new b1[0] is %c\n",b1[0]);
//printf("%s\n",b1);
if(index!='C')
{
if (sendto(fd,b1,sizeof(b1),0,(struct sockaddr *) &addr,sizeof(addr)) < 0)
{
perror("sendto");
exit(1);
}
//i++;
/*if(i>=4)
{
i=0;
}*/
sleep(1);
}
}
}
以下客户端代码在不同的系统上运行
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <string.h>
#include <stdio.h>
#include <stdio.h>
#include <mysql.h>
#define HELLO_PORT 12345
#define HELLO_GROUP "225.0.0.37"
#define MSGBUFSIZE 1024
main(int argc, char *argv[])
{
MYSQL mysql;
MYSQL_ROW row;
MYSQL_RES *result;
unsigned int num_fields;
unsigned int i;
mysql_init(&mysql);
struct sockaddr_in server;
int s,n;
char b1[100],b2[100],a[100];
char re[100]={0};
char g=" ";
printf("%c\n",re);
strcpy(b2,"1");
char message[20],ch='n';
struct sockaddr_in addr;
int fd, nbytes,addrlen,j=0;
struct ip_mreq mreq;
char msgbuf[MSGBUFSIZE];
u_int yes=1; /*** MODIFICATION TO ORIGINAL */
/* create what looks like an ordinary UDP socket */
if ((fd=socket(AF_INET,SOCK_DGRAM,0)) < 0)
{
perror("socket");
exit(1);
}
s=socket(AF_INET,SOCK_DGRAM,0);
server.sin_family=AF_INET;
server.sin_port=2000;
server.sin_addr.s_addr=inet_addr("10.42.0.1");
printf("\nClient ready....\n");
n=sizeof(server);
if (!mysql_real_connect(&mysql,"localhost","root","nidhi","project",0,NULL,0))
{
fprintf(stderr, "Failed to connect to database: Error: %s\n",
mysql_error(&mysql));
}
/**** MODIFICATION TO ORIGINAL */
/* allow multiple sockets to use the same PORT number */
if (setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(yes)) < 0)
{
perror("Reusing ADDR failed");
exit(1);
}
/*** END OF MODIFICATION TO ORIGINAL */
/* set up destination address */
memset(&addr,0,sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_addr.s_addr=htonl(INADDR_ANY); /* N.B.: differs from sender */
addr.sin_port=htons(HELLO_PORT);
/* bind to receive address */
if (bind(fd,(struct sockaddr *) &addr,sizeof(addr)) < 0)
{
perror("bind");
exit(1);
}
/* use setsockopt() to request that the kernel join a multicast group */
mreq.imr_multiaddr.s_addr=inet_addr(HELLO_GROUP);
mreq.imr_interface.s_addr=htonl(INADDR_ANY);
if (setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq)) < 0)
{
perror("setsockopt");
exit(1);
}
/* now just enter a read-print loop */
while (1)
{
/*if ((nbytes=recvfrom(fd,msgbuf,MSGBUFSIZE,0,(struct sockaddr *) &addr,&addrlen)) < 0)
{
perror("recvfrom");
exit(1);
}
printf("the server says: %s\n",msgbuf);*/
printf("would you like to send?(y/n)\n");
scanf("%c",&ch);
fflush(stdin);
if(ch=='y')
{
printf("\nClient:");
gets(a);
printf("%c\n",a);
strcat(b2,a);
printf("%s\n",b2);
sendto(s,b2,sizeof(b2),0,(struct sockaddr *) &server,n);
b2[100]=NULL;
strcpy(b2,"1");
}
addrlen=sizeof(addr);
if ((nbytes=recvfrom(fd,msgbuf,MSGBUFSIZE,0,(struct sockaddr *) &addr,&addrlen)) < 0)
{
perror("recvfrom");
exit(1);
}
printf("the server says: %s\n",msgbuf);
if(mysql_query(&mysql,msgbuf));
else
{
strcpy(re,"Client 1: ");
sendto(s,re,sizeof(re),0,(struct sockaddr *) &server,n);
//printf("inside else case\n");
result=mysql_store_result(&mysql);
//printf("\n after getting the result...\n");
num_fields = mysql_num_fields(result);
//printf("\n after getting numfields...\n");
while ((row = mysql_fetch_row(result)))
{
unsigned long *lengths;
//printf("\n inside while....\n");
lengths = mysql_fetch_lengths(result);
for(i = 0; i < num_fields; i++)
{
printf("[%.*s] \t", (int) lengths[i], row[i] ? row[i] : "NULL");
strcat(re,row[i]);
j++;
//printf("%d\n",j);
if(j==4)
{
//printf("the result is .....%s\n",re);
sendto(s,re,sizeof(re),0,(struct sockaddr *) &server,n);
memset(re,0,100);
strcpy(re,"Client 1: ");
j=0;
}
}
printf("\n");
}
}
}
}
我创建了一个adhoc网络，并为服务器和客户端分配了两个ip地址。 10.42.0.1/24到服务器，10.42.0.47 / 24到客户端
然而，从客户端到服务器的单播操作无法正常运行，也不是从服务器到客户端的多播。
其次，我如何确定这两个程序是否属于同一个多播组。客户端上的错误是
setsockopt：无效参数
或
setsockopt：没有这样的设备
对此有任何帮助，非常感谢.. !!
答案 0 :(得分：1)
您的代码中存在许多潜在错误：
服务器：
1.您没有检查's'套接字是否已成功创建。但是，您的示例将在没有它的情况下工作，因为有足够的内存用于创建套接字。
2.你没有检查bind（）的返回码，也许你不能将套接字绑定到端口，这就是你得到'无效参数'错误的原因
3.您没有检查recvfrom（）....
的返回码4. IP 255.0.0.37保留供将来使用，我不确定它是否有效，为什么不使用有效的IP范围？
5.对于多播，您必须使用范围内的IP地址：224.0.0.0/4，而不是10.0.0.0/8，因为它是为本地网络保留的。
关于客户端，您应首先制作udp协议代码，然后将mysql添加到其中。您还必须告诉我们您遇到错误的哪一行，否则很难分析问题。