Question

我正在编写一个基本的TCP客户端，我正在尝试连接到已经确定可行的TCP服务器。出于某种原因，我的客户端将无法连接到服务器。它不会通过连接尝试。客户端和服务器都在同一台机器上，我使用127.0.0.1和端口8080.任何指针为什么？谢谢！

/*
Usage: tcpclient <server_ip> <server_port> <client ip> <input_file> <output_file> <size of send/receive buffer>
*/

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

int main(int argc, char ** argv) {
    char* server_ip;
    char* client_ip;
    char* input_file; 
    char* output_file;
    int server_port, buffer_size;

    server_ip = argv[1];
    server_port = atoi(argv[2]);
    client_ip = argv[3];
    input_file = argv[4];
    output_file = argv[5];
    buffer_size = atoi(argv[6]);

    int sockfd = 0;
    int bitsSent = 0;
    int bitsReceived = 0;

    char sendBuffer[buffer_size];
    char recvBuffer[buffer_size];

    struct sockaddr_in serv_addr;

    memset(recvBuffer, '0', sizeof(recvBuffer));
    memset(sendBuffer, '0', sizeof(sendBuffer));
    memset((char *)&serv_addr,0,sizeof(serv_addr)); 


    /* Check command line arguments */
    if (argc != 7) {    
        exit(0);
    }

    /* Create the socket */
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0))< 0)
    {
        printf("\n Error : Could not create socket \n");
        return 1;
    }

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(server_port);
    serv_addr.sin_addr.s_addr = inet_addr(server_ip);

    /* Attempt to connect to server */
    if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr))<0) {
        printf("Err: Couldn't connect");
        return 1;
    }   

    /* Open the input file to read */
    FILE *fp;
    fp = fopen(input_file, "r");

    if (fp == NULL) {
        perror("Error opening the file");
        return(-1);
    }

    /* Receive the data then write to sendBuffer */
    while ((bitsSent = read(sockfd, recvBuffer, buffer_size)) >0) {
        printf("Bytes received: %d\n", bitsReceived);
        fwrite(recvBuffer, 1, bitsReceived, fp);
    }

    if (bitsReceived < 0) {
        printf("Read Error");
    }

    return 0;

}

Answer 1

在创建套接字之前，您正尝试connect。由于此时sockfd为零，因此您尝试connect标准输入。

Answer 2

我不记得那是否相关，而不是：

serv_addr.sin_addr.s_addr = inet_addr(server_ip);

尝试：

inet_aton("127.0.0.1",&server_addr.sin_addr);

正如另一个回复说你忘了创建套接字：

if((sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0){
    perror("Error al crear el socket");
    exit(1);
}

C TCP客户端将无法连接到服务器

2 个答案: