简单的网络编程程序 - 无法正常工作

Question

我刚开始学习网络编程.我的第一个程序非常简单:一旦连接,服务器程序显示客户端程序发送的内容(字符).一切正常,直到他们连接起来.起初,我使用putc完成了发送循环:

while((c = getc(stdin)) != '\n')
    putc(c, (FILE *) connection);

并使用getc接收一个:

while((c = getc((FILE *) connection)) != '\n')
    putc(c, stdout);

连接后,我遇到了分段错误.然后我尝试使用发送:

while(1) {
    memset(str, null, strlen(memset));

    while(((c = getc(stdin)) != '\n') && sizeof(str) <= 100) {
        strcat(str, (char *) c);       // cast to char * is to make gcc happy
    }

    send(connection, (void *) str, sizeof(str), (int) NULL);
}

和recv:

while((stat = recv(connection,str,100,0)) != 0) {
    printf("\nReceived %d bytes of data from %s: %s", stat, client, str);
}

现在recv()保持返回-1并且errno设置为107.这是什么意思？我哪里做错了？顺便说一下,我正在使用Linux和gcc.

非常感谢你的帮助!:)

---

编辑:即使我使用getc()和putc(),我得到socket()的连接,然后我连接()(客户端).服务器在获得连接(使用socket())bind()之后,然后是listen()和accept().对不起,如果我捣蛋.

---

这是服务器代码:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <arpa/inet.h>
#include <netdb.h>

void main(int argc, char *argv[])
{
    struct addrinfo hint;
    struct addrinfo *servinfo, *count;
    struct sockaddr_storage conn_addr;
    struct sockaddr host;

    int connessione;
    int stat;
    int conn_sock;
    int conn_size;
    int success;
    int c;

    char t[INET_ADDRSTRLEN];
    char str[100];
    char *client;

    if(argc != 1 && strcmp(argv[1], "aiuto") == 0) {
        printf("%s(porta)\n",argv[0]);
        printf("porta: specifica su quale porta installarsi\n");
        exit(-1);
    }

    memset(&hint,0,sizeof hint);


    hint.ai_family = AF_INET;
    hint.ai_socktype = SOCK_STREAM;
    hint.ai_flags = AI_PASSIVE;

    if((stat = getaddrinfo(NULL, argv[1], &hint, &servinfo)) != 0)  {
        printf("\n[FATAL]: getaddrinfo: %s",gai_strerror(stat));
        exit(-1);
    }

    success = 0;

    for(count = servinfo; count != NULL; count = count->ai_next) {
        if((connessione = socket(count->ai_family, count->ai_socktype, count->ai_protocol)) <= 0)
            continue;

        if((stat = bind(connessione, count->ai_addr, count->ai_addrlen)) == 0) {
            success = 1;
            break;
        }
        else {
            continue;
        }
    }

    if(success == 0) {
        printf("\n[FATAL]: Unable to bind()!\n");
        exit(-1);
    }
    else {
        printf("\n[DEBUG]: %s: listening...", argv[0]);
    }

    servinfo = count;
    freeaddrinfo(count);

    if(listen(connessione, 20) == -1) {
        printf("\n[FATAL]: listen: %s (%d)\n", gai_strerror(errno), errno);
        close(connessione);
        exit(-1);
    }

    conn_size = sizeof(conn_addr);

    if(accept(connessione, (struct sockaddr *) &conn_addr, &conn_size) == -1) {
        printf("\n[FATAL]: accept: %s", gai_strerror(errno));
        close(connessione);
        exit(-1);
    }

    client = (char *) malloc(INET_ADDRSTRLEN * sizeof(char));
    client = inet_ntop(servinfo->ai_family, &conn_addr, t, INET_ADDRSTRLEN);

    printf("\n[DEBUG]: %s: connection accepted: %s", argv[0], client);

    while((stat = recv(connessione,str,100,0)) != 0) {
        printf("\nReceived %d bytes of data from %s: %s", stat,client, str);
    }

    printf("\n[DEBUG]: connection closed by %s\n",client);
}

和客户的代码:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <arpa/inet.h>
#include <netdb.h>

void main(int argc, char *argv[])
{
    struct addrinfo hint;
    struct addrinfo *servinfo, *count;
    struct sockaddr_storage conn_addr;
    struct sockaddr host;

    int connessione;
    int stat;
    int conn_sock;
    int conn_size;
    int success;
    int c;

    char t[INET_ADDRSTRLEN];
    char *indirizzo;
    char str[100];

    memset(&hint,0,sizeof hint);

    host.sa_family = AF_INET;
    if(inet_pton(host.sa_family, argv[1], (void *) host.sa_data) == -1) {
        printf("\n[FATAL]: pton: %s (%d)\n", gai_strerror(errno), errno);
        exit(-1);
    }

    hint.ai_family = AF_INET;
    hint.ai_socktype = SOCK_STREAM;
    hint.ai_flags = AI_PASSIVE;
    hint.ai_addr = &host;

    if((stat = getaddrinfo(argv[1], argv[2], &hint, &servinfo)) != 0)  {
        printf("[FATAL]: getaddrinfo: %s\n",gai_strerror(stat));
        exit(-1);
    }

    success = 0;
    for(count = servinfo; count != NULL; count = count->ai_next) {
        if((connessione = socket(count->ai_family, count->ai_socktype, count->ai_protocol)) == -1)
            continue;

        if(connect(connessione, count->ai_addr, count->ai_addrlen) != -1) {
            success = 1;
            break; 
        }
    }

    if(success == 0) {
        printf("\n[FATAL]: impossibile trovare l'host specificato\n");
        exit(-1);
    }

    servinfo = count;
    freeaddrinfo(count);

    indirizzo = (char *) malloc(INET_ADDRSTRLEN * sizeof(char));
    indirizzo = inet_ntop(servinfo->ai_family, &conn_addr, t, INET_ADDRSTRLEN);

    printf("\n[DEBUG]: %s: connesso a: %s\n",argv[0], indirizzo);

    while(1) {
        strcpy(str,"buffer for data to send");

        while(((c = getc(stdin)) != '\n') && sizeof(str) <= 100) {
            strcat(str, (char *) c);
        }

        send(connessione, (void *) str, sizeof(str), (int) NULL);
    }
}

---

在末尾...

它完美无缺!感谢大家.:)

Answer 1

通常,您不使用FILE *句柄进行网络编程.相反,您需要socket(2)系统调用返回的套接字描述符.一旦拥有它,您可以connect(2)(客户端)或bind(2)它(服务器).可以使用recv(2)和执行正在进行的通信send(2).

如果您真的想使用FILE *句柄进行网络编程,请查看fdopen(3)库函数.它需要一个可以返回的描述符,socket(2)并返回一个FILE *与fread/ fwrite/ 兼容的句柄fprintf.

发布完整代码后,我看到的最重要的错误是:

if (accept(connessione, (struct sockaddr *) &conn_addr, &conn_size))

accept(2)返回一个必须与recv(2)/一起send(2)使用的套接字,然后使用服务器套接字丢弃它.