c socket編程，接收線路錯誤

Question

我在C.My中使用Socket編程修改了一個簡單的聊天程序的代碼，問題是我必須在服務器或客戶端輸入兩行來接收另一行我已經上傳了一張圖片來解釋更多。任何幫助表示讚賞

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

你只發送/ recieving每次30個字節。也許這應該是BUFLEN？更好的是，在消息的前面有一個固定大小的塊，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); 

客戶：

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

錯誤檢查已經爲清楚起見被省略。

Answer 2

據我所知，你想逐一讀一行。但是，recv（）函數不會將消息逐個傳遞給您，因爲它只從消息流中讀取一定數量的數據。爲了區分消息，有兩種方法。

首先，您發送固定大小的消息（本例中爲30個字節），並始終從網絡的其他位置讀取30個字節。其次，用包含數據長度的結構封裝數據，以提供各種大小的消息。這種方法更好，因爲如果你想發送-let的說 - 1024字節長的字符串，別人會知道它並相應地讀取1024個字節。

Answer 3

我必須做錯了什麼，我已經將大小添加到標頭消息，並且現在沒有從客戶端和服務器接收任何數據。我正確使用它。 這裏是我插入大小的代碼的一部分。

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; 
}