Linux套接字錯誤文件描述符

Question

我找不到重複的，所以我決定發佈。我們現在進入套接字（初學者級別），並獲得了下面的代碼，使客戶端通過使用send()和recv()向服務器發送簡單消息。但是，我所嘗試過的所有東西似乎都沒有擺脫error: Bad File Descriptor和newsockfd始終返回值-1。我很困惑，不知道爲什麼它不起作用。

的defs.h

#include <stdio.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <arpa/inet.h> 

#define SERV_TCP_PORT 6000 
#define SERV_HOST_ADDR "127.0.0.1" 

char *pname; 

client.c

#include "../defs.h" 
#include <stdio.h> 
#include <stdlib.h> 
#include <strings.h> 

main(argc, argv) 
int argc; 
char *argv[]; 
{ 
    int sockfd; 
    struct sockaddr_in serv_addr; 

    pname=argv[0]; 
    bzero((char*) &serv_addr, sizeof(serv_addr)); 
    serv_addr.sin_family=AF_INET; 
    serv_addr.sin_addr.s_addr=inet_addr(SERV_HOST_ADDR); 
    serv_addr.sin_port=htons(SERV_TCP_PORT); 
    if((sockfd=socket(AF_INET,SOCK_STREAM,0)) < 0) { 
    printf("client: can't open stream socket\n"); 
    exit(0); 
    } 
    if (connect(sockfd,(struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) { 
    printf("client: can't connect to server\n"); 
    exit(0); 
    } 
send(sockfd,"1",1,0); 
    close(sockfd); 
    exit(0); 
} 

server.c

#include "../defs.h" 
#include <stdio.h> 
#include <stdlib.h> 
#include <sys/socket.h> 
#include <strings.h> 
void error(char *msg) 
{ 
    perror(msg); 
    exit(1); 
} 
main(argc, argv) 
int argc; 
char *argv[]; 
{ 
    int sockfd,clilen, childpid; 
int newsockfd; 
char buff[255]; 
    struct sockaddr_in cli_addr, serv_addr; 
    if ((sockfd=socket(AF_INET,SOCK_STREAM, 0)) <0) { 
    printf("server: can't open stream socket\n"); 
    exit(0); 
    } 
    bzero((char*) &serv_addr, sizeof(serv_addr)); 
    serv_addr.sin_family=AF_INET; 
    serv_addr.sin_addr.s_addr=htonl(INADDR_ANY); 
    serv_addr.sin_port=htons(SERV_TCP_PORT); 

    if(bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) { 
    printf("server: can't bind local address\n"); 
    exit(0); 
    } 
    listen(sockfd, 5); 
    for (; ;) { 
    clilen=sizeof(cli_addr); 
    newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen); 
    printf("%d\n",newsockfd); 
    if(newsockfd < 0) { 
     printf("server: accept error\n"); 
    error("ERROR on accept"); 
     exit(0); 
    } 
    if((childpid=fork()) <0) { 
     printf("server: fork error\n"); 
     exit(0); 
    } 
    else if (childpid==0) { 
     close(sockfd); 
     recv(newsockfd,buff,sizeof(buff),0); 
    } 
    close(newsockfd); 
    } 
} 

感謝您的時間。

Answer 1

在孩子的代碼你關閉sockfd，它代表服務器。但在無限for循環的下一次迭代中，孩子也運行，您嘗試使用sockfdaccept()新客戶端。因此，sockfd是Bad file descriptor。

刪除代碼中的close(sockfd);行，並在可以絕對確定它不再需要時關閉它。