c socket编程，接收线路错误

Question

我在C.My中使用Socket编程修改了一个简单的聊天程序的代码，问题是我必须在服务器或客户端输入两行来接收另一行我已经上传了一张图片来解释更多。任何帮助表示赞赏

SERVER 
#include <stdio.h> 
#include <sys/types.h> 
#include<sys/socket.h> 
#include<netinet/in.h> 
#include<stdlib.h> 
#include<strings.h> 
#include<unistd.h> 
#define SERVER_TCP_PORT 3000 
#define BUFLEN 256 

int main (int argc,char **argv) 
{ 
    int n,bytes_to_read; 
    int sd,new_sd,client_len,port; 
    struct sockaddr_in server,client; 
    char *bp,buf[BUFLEN]; 

    switch (argc) { 
     case 1: 
      port = SERVER_TCP_PORT; 
      break; 
     case 2: 
      port = atoi (argv[1]); 
      break; 
     default: 
      fprintf (stderr,"Usage: %s[port]\n",argv[0]); 
      exit(1); 
      } 
    /*Create a system socket */ 

     if ((sd = socket(AF_INET,SOCK_STREAM,0))==-1){ 
      fprintf(stderr,"Can't create a socket\n"); 
      exit(1); 
      } 

    /*Bind an address to the socket*/ 

    bzero ((char*)&server,sizeof(struct sockaddr_in)); 
    server.sin_family = AF_INET; 
    server.sin_port = htons(port); 
    server.sin_addr.s_addr = htonl(INADDR_ANY); 
    if(bind(sd,(struct sockaddr *)&server,sizeof(server))==-1){ 
     fprintf(stderr,"can't bind name to socket\n"); 
     exit(1); 
    } 
    /*queue up to 5 connect requests*/ 

    listen(sd,5); 
    while(1){ 
     client_len = sizeof(client); 
    if((new_sd = accept(sd,(struct sockaddr *)&client,&client_len))==-1){ 
     fprintf(stderr,"can't accept client \n"); 
     exit(1); 
     } 

if(fork()) 
{ 
printf("\n Server listening to clients on port 2000"); 
printf("\n Server got request from%s",inet_ntoa(client.sin_addr)); 
printf("\n SEND DATA<q or Q to quit> :%s",buf); 
scanf("%s",buf); 
while((strcmp(buf,"q")!=0)&&(strcmp(buf,"Q")!=0)) 
{ 
send(new_sd,buf,30,0); 
scanf("%s",buf); 

} 
send(new_sd,"q",5,0); 
} 
else{ 
n = recv(new_sd,buf,30,0); 
while((strcmp(buf,"q")!=0)&&(strcmp(buf,"Q")!=0)) 
{ 
printf("\nRECEIVED DATA =%s",buf); 
n = recv(new_sd,buf,30,0); 

} 
printf("\n Bye"); 
send(new_sd,"EOF",4,0); 
close(sd); 
close(new_sd); 
} 
} 
return 0; 
} 



Client 
#include <stdio.h> 
#include <sys/types.h> 
#include<sys/socket.h> 
#include <netdb.h> 
#include<stdlib.h> 
#include<strings.h> 
#include <netinet/in.h> 

#define SERVER_TCP_PORT 3000 
#define BUFLEN 256 
int main(int argc,char **argv) 
{ 

int n,bytes_to_read; 
int sd,port; 
struct hostent *hp; 
struct sockaddr_in server; 
char *host,*bp,rbuf[BUFLEN],sbuf[BUFLEN]; 
switch(argc) { 
    case 2: 
     host = argv[1]; 
     port = SERVER_TCP_PORT; 
     break; 
    case 3: 
     host = argv[1]; 
     port = atoi(argv[2]); 
     break; 
    default: 
     fprintf(stderr,"Usage: %s host[port] \n",argv[0]); 
     exit(1); 
     } 

/*Create a stream socket*/ 

if ((sd=socket(AF_INET,SOCK_STREAM,0))==-1){ 
    fprintf(stderr,"Can't create a socket\n"); 
    exit(1); 
    } 
bzero ((char *)&server,sizeof(struct sockaddr_in)); 
server.sin_family = AF_INET; 
server.sin_port = htons(port); 
if((hp = gethostbyname(host))==NULL){ 
    fprintf (stderr,"Can't get server's address\n"); 
    exit(1); 
    } 
bcopy(hp->h_addr,(char *)&server.sin_addr,hp->h_length); 
/*connecting to the server*/ 

if (connect (sd,(struct sockaddr *)&server,sizeof(server))==-1){ 
    fprintf(stderr,"Can't connect \n"); 
    exit(1); 
    } 
printf("Connected:server's address is %s\n",hp->h_name); 

if(fork()) 
{ 
bzero(rbuf,30); 
printf("\n SEND DATA<q or Q to quit> :%s",rbuf); 
scanf("%s",rbuf); 
while((strcmp(rbuf,"q")!=0)&&(strcmp(rbuf,"Q")!=0)) 
{ 
send(sd,rbuf,30,0); 
scanf("%s",rbuf); 

} 
send(sd,"q",5,0); 
} 

else{ 
n = recv(sd,rbuf,30,0); 
while((strcmp(rbuf,"q")!=0)&&(strcmp(rbuf,"Q")!=0)) 
{ 
printf("\nRECEIVED DATA =%s",rbuf); 
n = recv(sd,rbuf,30,0); 

} 
printf("\n Bye"); 
send(sd,"EOF",4,0); 
close(sd); 
} 

return 0; 
} 

Answer 1

你只发送/ recieving每次30个字节。也许这应该是BUFLEN？更好的是，在消息的前面有一个固定大小的块，其中包括消息的strlen。

例如：

int size = htonl(strlen(buf)+1); 
send(new_sd, size, sizeof(size), 0); 
send(new_sd, buf, size, 0); 

客户：

int size; 
recv(sd, size, sizeof(size),0); 
size = ntohl(size); 
recv(sd, buf, size, 0); 

错误检查已经为清楚起见被省略。

Answer 2

据我所知，你想逐一读一行。但是，recv（）函数不会将消息逐个传递给您，因为它只从消息流中读取一定数量的数据。为了区分消息，有两种方法。

首先，您发送固定大小的消息（本例中为30个字节），并始终从网络的其他位置读取30个字节。其次，用包含数据长度的结构封装数据，以提供各种大小的消息。这种方法更好，因为如果你想发送-let的说 - 1024字节长的字符串，别人会知道它并相应地读取1024个字节。

Answer 3

我必须做错了什么，我已经将大小添加到标头消息，并且现在没有从客户端和服务器接收任何数据。我正确使用它。 这里是我插入大小的代码的一部分。

SERVER

if(fork()) 
{ 
printf("\n Server listening to clients on port 2000"); 
printf("\n Server got request from%s",inet_ntoa(client.sin_addr)); 
bzero(buf,256); 
printf("\n SEND DATA<q or Q to quit> :%s",buf); 
scanf("%s",buf); 
while((strcmp(buf,"q")!=0)&&(strcmp(buf,"Q")!=0)) 
{ 
int size = htonl(strlen(buf)+1); 
send(new_sd,size,sizeof(size),0); 
send(new_sd,buf,size,0); 
scanf("%s",buf); 

} 
send(new_sd,"q",5,0); 
} 
else{ 

int size; 
recv(new_sd,size,sizeof(size),0); 
size=ntohl(size); 
n=recv(new_sd,buf,size,0); 
while((strcmp(buf,"q")!=0)&&(strcmp(buf,"Q")!=0)) 
{ 
printf("\nRECEIVED DATA =%s",buf); 
n = recv(new_sd,buf,size,0); 
} 
printf("\n Bye"); 
send(new_sd,"EOF",BUFLEN,0); 
close(sd); 
close(new_sd); 
} 
} 
return 0; 
} 

CLIENT

if(fork()) 
{ 
printf("\n SEND DATA<q or Q to quit> :%s",rbuf); 
scanf("%s",rbuf); 
while((strcmp(rbuf,"q")!=0)&&(strcmp(rbuf,"Q")!=0)) 
{ 
int size = htonl(strlen(sbuf)+1); 
send(sd,size,sizeof(size),0); 
send(sd,sbuf,size,0); 
scanf("%s",sbuf); 

} 
send(sd,"q",5,0); 
} 

else{ 
int size; 
recv(sd,size,sizeof(size),0); 
size = ntohl(size); 
recv(sd,rbuf,size,0); 
while((strcmp(rbuf,"q")!=0)&&(strcmp(rbuf,"Q")!=0)) 
{ 
printf("\nRECEIVED DATA =%s",rbuf); 
//n = recv(sd,rbuf,bytes_to_read,0); 

} 
printf("\n Bye"); 
send(sd,"EOF",4,0); 
close(sd); 
} 

return 0; 
}