[英]bad file descriptor: error on accept() (socket)
我正在尝试在 Linux 中使用 TCP 协议编写一个简单的聊天应用程序,其中服务器从客户端接收字符串并将字符串大小发送到客户端。 当我运行客户端时,服务器抛出“错误的文件描述符”错误并退出。 尽管如此,如果我通过客户端发送输入字符串,它会收到正确大小的字符串,但正如我在服务器关闭之前所说的那样。 这是代码:
服务器
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#define MAX_LINE 1024
int main(int argc, char const *argv[]) {
int listen_fd, connect_fd, logging, str_lenght;
struct sockaddr_in serv_addr, client;
char buffer_str[MAX_LINE], buffer[MAX_LINE];
pid_t pid;
socklen_t len;
logging = 1;
if ((listen_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket");
exit(-1);
}
bzero(&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(1024);
if (bind(listen_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
perror("bind");
exit(-1);
}
if (listen(listen_fd, 1024) < 0) {
perror("listen");
exit(-1);
}
for (;;) {
len = sizeof(client);
if ((connect_fd = accept(listen_fd, (struct sockaddr *)&client, &len)) < 0) {
perror("accept");
exit(-1);
}
if ((pid = fork()) < 0) {
perror("fork");
exit(-1);
}
if (pid == 0) {
close(listen_fd);
for (;;) {
bzero(buffer_str, MAX_LINE);
if (read(connect_fd, buffer_str, sizeof(buffer_str)) < 0) {
perror("read");
exit(-1);
}
if (strcmp(buffer_str, "exit") == 0) break;
str_lenght = (int)strlen(buffer_str) - 1;
bzero(buffer_str, MAX_LINE);
snprintf(buffer_str, sizeof(buffer_str), "%d\n", str_lenght);
if (write(connect_fd, buffer_str, sizeof(buffer_str)) < 0) {
perror("write");
exit(-1);
}
if (logging) {
inet_ntop(AF_INET, &client.sin_addr, buffer, sizeof(buffer));
printf("Request from host %s, port %d\n", buffer, ntohs(client.sin_port));
}
}
close(connect_fd);
exit(0);
} else close(listen_fd);
}
exit(0);
}
客户
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#define MAX_LINE 1024
void clientEcho(int socket_fd) {
char recv_buffer[MAX_LINE], send_buffer[MAX_LINE];
for (;;) {
bzero(recv_buffer, MAX_LINE);
bzero(send_buffer, MAX_LINE);
printf("insert string: ");
if (fgets(send_buffer, sizeof(send_buffer), stdin) == NULL) {
perror("fgets");
return;
}
if (write(socket_fd, send_buffer, sizeof(send_buffer)) < 0) {
perror("write");
return;
}
if (strcmp(send_buffer, "exit") == 0) break;
if (read(socket_fd, recv_buffer, sizeof(recv_buffer)) < 0) {
perror("read");
return;
}
printf("string size: ");
if (fputs(recv_buffer, stdout) < 0) {
perror("fputs");
return;
}
}
}
int main(int argc, char const *argv[]) {
int socket_fd;
struct sockaddr_in serv_addr;
if (argc != 2) {
perror("usage: <IPaddress>");
exit(-1);
}
if ((socket_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket");
exit(-1);
}
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(1024);
if (inet_pton(AF_INET, argv[1], &serv_addr.sin_addr) <= 0) {
perror("inet_pton");
exit(-1);
}
if (connect(socket_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
perror("connect");
exit(-1);
}
clientEcho(socket_fd);
close(socket_fd);
exit(0);
}
根据评论。 您的服务器代码基本上如下...
if (listen(listen_fd, 1024) < 0) {
perror("listen");
exit(-1);
}
for (;;) {
len = sizeof(client);
if ((connect_fd = accept(listen_fd, (struct sockaddr *)&client, &len)) < 0) {
perror("accept");
exit(-1);
}
if ((pid = fork()) < 0) {
perror("fork");
exit(-1);
}
if (pid == 0) {
...
exit(0);
} else {
close(listen_fd); /* @Here */
}
}
exit(0);
吃了标有@Here
你关闭监听文件描述符listen_fd
@Here
行,意思是下一个……
connect_fd = accept(listen_fd, (struct sockaddr *)&client, &len)
由于listen_fd
无效, for (;;)
循环中的调用将失败。
您随后的评论表明这可能不是唯一的问题,但我很确定它是导致bad file descriptor: error on accept()
错误消息bad file descriptor: error on accept()
错误。
除了其他答案所说的内容之外:您永远不会发送"exit"
字符串,而是"exit\\n"
(即后跟一个新文件 -和1019 个零字节)和strcmp(buffer_str, "exit") == 0
在服务器中永远不会为真。
顺便说一句,这段代码被破坏了:
bzero(buffer_str, MAX_LINE);
if (read(connect_fd, buffer_str, sizeof(buffer_str)) < 0) {
perror("read");
exit(-1);
}
if (strcmp(buffer_str, "exit") == 0) break;
str_lenght = (int)strlen(buffer_str) - 1;
如果read
返回的正好是sizeof(buffer_str)
个字节,则缓冲区可能不是以零结尾的,并且您不能在其上使用strcmp
。 而且我不认为将str_lenght
(sic) 设置为比字符串的实际长度少 1 的意义。
谢谢每一位。 此代码运行:
服务器
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#define MAX_LINE 1024
int main(int argc, char const *argv[]) {
int listen_fd, connect_fd, logging, str_lenght;
struct sockaddr_in serv_addr, client;
char buffer_str[MAX_LINE], buffer[MAX_LINE];
pid_t pid;
socklen_t len;
logging = 1;
if ((listen_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket");
exit(-1);
}
bzero(&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(1024);
if (bind(listen_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
perror("bind");
exit(-1);
}
if (listen(listen_fd, 1024) < 0) {
perror("listen");
exit(-1);
}
for (;;) {
len = sizeof(client);
if ((connect_fd = accept(listen_fd, (struct sockaddr *)&client, &len)) < 0) {
perror("accept");
exit(-1);
}
if ((pid = fork()) < 0) {
perror("fork");
exit(-1);
}
if (pid == 0) {
for (;;) {
bzero(buffer_str, MAX_LINE);
if (read(connect_fd, buffer_str, sizeof(buffer_str)) < 0) {
perror("read");
exit(-1);
}
if (strcmp(buffer_str, "exit\n") == 0) break;
str_lenght = (int)strlen(buffer_str) - 1;
bzero(buffer_str, MAX_LINE);
snprintf(buffer_str, sizeof(buffer_str), "%d\n", str_lenght);
if (write(connect_fd, buffer_str, sizeof(buffer_str)) < 0) {
perror("write");
exit(-1);
}
if (logging) {
inet_ntop(AF_INET, &client.sin_addr, buffer, sizeof(buffer));
printf("Request from host %s, port %d\n", buffer, ntohs(client.sin_port));
}
}
close(connect_fd);
exit(0);
} else close(connect_fd);
}
exit(0);
}
客户
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#define MAX_LINE 1024
void clientEcho(int socket_fd) {
char recv_buffer[MAX_LINE], send_buffer[MAX_LINE];
for (;;) {
bzero(recv_buffer, MAX_LINE);
bzero(send_buffer, MAX_LINE);
printf("insert string: ");
if (fgets(send_buffer, sizeof(send_buffer), stdin) == NULL) {
perror("fgets");
return;
}
if (write(socket_fd, send_buffer, sizeof(send_buffer)) < 0) {
perror("write");
return;
}
if (strcmp(send_buffer, "exit\n") == 0) break;
if (read(socket_fd, recv_buffer, sizeof(recv_buffer)) < 0) {
perror("read");
return;
}
printf("string size: ");
if (fputs(recv_buffer, stdout) < 0) {
perror("fputs");
return;
}
}
}
int main(int argc, char const *argv[]) {
int socket_fd;
struct sockaddr_in serv_addr;
if (argc != 2) {
perror("usage: <IPaddress>");
exit(-1);
}
if ((socket_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket");
exit(-1);
}
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(1024);
if (inet_pton(AF_INET, argv[1], &serv_addr.sin_addr) <= 0) {
perror("inet_pton");
exit(-1);
}
if (connect(socket_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
perror("connect");
exit(-1);
}
clientEcho(socket_fd);
close(socket_fd);
exit(0);
}
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