使用Linux socketAPI 实现图片的网络传输

服务端：

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

#define MAXLINE 409600

int main(int argc, char** argv)
{
    if(argc < 3)
    {
        printf("usage: ./%s <ip> <port>\n", basename(argv[0]));
        return 1;
    }

    const char *ip = argv[1];
    int port = atoi(argv[2]);

    int listenfd;
    if( (listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1 ){
        printf("create socket error: %s(errno: %d)\n",strerror(errno),errno);
        return 0;
    }
    printf("----init socket----\n");

    struct sockaddr_in  servaddr;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(port);
    inet_pton(AF_INET, ip, &servaddr.sin_addr);


    //设置端口可重用
    int contain;
    setsockopt(listenfd,SOL_SOCKET, SO_REUSEADDR, &contain, sizeof(int));

    if( bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) == -1){
        printf("bind socket error: %s(errno: %d)\n",strerror(errno),errno);
        return 0;
    }
    printf("----bind sucess----\n");

    if( listen(listenfd, 10) == -1){
        printf("listen socket error: %s(errno: %d)\n",strerror(errno),errno);
        return 0;
    }

    FILE *fp;
    if((fp = fopen("new1.jpg","ab") ) == NULL )
    {
        printf("File.\n");
        close(listenfd);
        exit(1);
    }

    printf("======waiting for client's request======\n");
    int connfd;
    char  buff[MAXLINE];
    while(1){
        struct sockaddr_in client_addr;
        socklen_t size=sizeof(client_addr);
        // 调试时注意阻塞函数,如accept
        if( (connfd = accept(listenfd, (struct sockaddr*)&client_addr, &size)) == -1){
            printf("accept socket error: %s(errno: %d)",strerror(errno),errno);
            continue;
        }
        int n;
        while(1){
            n = recv(connfd, buff, MAXLINE, 0);
            if(n == 0)
            {
                printf("n == 0, close connect.\n");
                break;
            }
            else if( n < 0)
            {   // #define	EFAULT		14	/* Bad address */
                printf("ERR: errno is %d\n", errno);
                break;
            }
            fwrite(buff, 1, n, fp);
        }
        buff[n] = '\0';
        printf("recv msg from client: %s\n", buff);
        close(connfd);
        fclose(fp);
    }
    close(listenfd);
    return 0;
}

客户端：

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

#define MAXLINE 409600

int main(int argc, char** argv)
{
    if( argc != 3){
        printf("usage: ./%s <ipaddress> <port>\n", basename(argv[0]));
        return 0;
    }

    const char *ip = argv[1];
    int port = atoi(argv[2]);

    int   sockfd;
    if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        printf("create socket error: %s(errno: %d)\n", strerror(errno),errno);
        return 0;
    }

    struct sockaddr_in  servaddr;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(port);
    if( inet_pton(AF_INET, ip, &servaddr.sin_addr) <= 0){
        printf("inet_pton error for %s\n",argv[1]);
        return 0;
    }

    if( connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0){
        printf("connect error: %s(errno: %d)\n",strerror(errno),errno);
        return 0;
    }
    // "r"  "a"  "w" 是针对文本文件的处理
    // "rb"  "ab"  "wb" 都是针对二进制文件的处理(在POSIX系统上其实并无区别)
    FILE *fq;
    if( ( fq = fopen("test1.jpg","rb") ) == NULL ){
        printf("File open.\n");
        close(sockfd);
        exit(1);
    }

    char  buffer[MAXLINE];
    int   len;
    memset(buffer,'\0',sizeof(buffer));
    while(!feof(fq)){
        len = fread(buffer, 1, sizeof(buffer), fq);
        int rest = len;
        while (rest > 0)
        {
            int send_ret = send(sockfd, buffer, len, 0);
            rest -= send_ret;
        }
    }
    close(sockfd);
    fclose(fq);

    return 0;
}

注：

1. 对二进制文件的读写最好使用fread/fwrite两个标准C函数

2. 对于二进制文件，一定要注意文件的大小(有可能具有成千上万bytes)

3. 对于socket TCP通信最好用recv()/send()来接收/发送数据