问题描述

网络编程新手求指导---客户端为何write()始终返回0

在本机上做实验，客户端输入文字在服务器端显示

客户端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

#define portnumber 3333

int main(int argc, char *argv[])
{
    int sockfd, nwrite=0;
    char buffer[1024];
    struct sockaddr_in server_addr;
    struct hostent *host;

    /*检查输入格式*/
    if(argc != 2)
    {
        fprintf(stderr,"Usage: %s hostnamen",argv[0]);
        exit(1);
    }

    /*使用hostbyname获取host名字*/
    if((host = gethostbyname(argv[1])) == NULL)
    {
        fprintf(stderr,"gethostname error!n");
        exit(1);
    }

    /*建立socket描述符*/
    if((sockfd = socket(AF_INET,SOCK_STREAM,0)) == -1)
    {
        fprintf(stderr,"Socket error!n");
        exit(1);
    }

    /*客户程序填充服务器端资料*/
    bzero(&server_addr,sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port    = htons(portnumber);
    server_addr.sin_addr    = *((struct in_addr *)host->h_addr);

    /*客户端发起连接*/
    if(connect(sockfd,(struct sockaddr *)(&server_addr),
       sizeof(struct sockaddr)) == -1)
    {
        fprintf(stderr,"fail to connect!%sn", strerror(errno));
        exit(1);
    }

    /*链接成功*/
    printf("Please input char:n");

    /*发送数据*/
    fgets(buffer,1024,stdin);
    printf("%s", buffer);
    if((nwrite = write(sockfd,buffer,strlen(buffer)) == -1))
    {
        printf("write error!n");
    }
    printf("nwrite = %dn", nwrite);//为何一直返回0 ？写不进去？
    /*关闭连接*/
    close(sockfd);

    exit(0);

}

服务器端

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

#define portnumber 3333

int main(int argc, char *argv[])
{
    int sockfd;
    int nbytes;
    int sin_size;
    int new_fd;
    char buffer[1024];
    struct sockaddr_in server_addr;
    struct sockaddr_in client_addr;

    /*服务端创建套接字*/
    if((sockfd = socket(AF_INET,SOCK_STREAM,0)) == -1)
    {
        fprintf(stderr, "Create socket error!n");
        exit(1);
    }

    /*结构清零*/
    bzero(&server_addr, sizeof(struct sockaddr_in));
    {
        server_addr.sin_family      = AF_INET;
        server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
        server_addr.sin_port        = htons(portnumber);
    }

    /*绑定结构*/
    if(bind(sockfd, (struct sockaddr *)(&server_addr), sizeof(struct sockaddr)) == -1)
    {
        fprintf(stderr, "Bind error! %sn", strerror(errno));
        exit(1);
    }

    /*监听套接口设置最大监听个数*/
    if(listen(sockfd,5) == -1)
    {
        fprintf(stderr, "listen setting error!n");
        exit(1);
    }

    while(1)
    {
        sin_size = sizeof(struct sockaddr_in);
        if(new_fd = accept(sockfd, (struct sockaddr *)(&client_addr), &sin_size) == -1)
        {
            fprintf(stderr, "accept error!n");
            exit(1);
        }

        /*与客户端连接成功*/
        fprintf(stderr, "Server get connction from %sn", inet_ntoa(client_addr.sin_addr));
        if((nbytes = read(new_fd, buffer, 1024)) == -1)
        {
            fprintf(stderr, "read error!n");
            exit(1);
        }

        buffer[nbytes] = '';

        printf("Received from client %s : %s", inet_ntoa(client_addr.sin_addr), buffer);

        close(new_fd);

    }

    close(sockfd);

    exit(0);

}

运行结果：

解决方案

括号那里改一下试试 nwrite = write(sockfd,buffer,strlen(buffer))；
if( ..... )
......