添加代码

这是个很常见的问题：在bind函数之前添加如下代码即可。 

    int yes = 1;  
    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) {  
        perror("setsockopt");  
        exit(1);  
    } 

查看端口

如果还是不能结果，那么说明是真的冲突了，例如查看当前UDP ipv4使用的端口号，如下所示：如果发现端口已被使用，则kill掉相关进程，或者使用其他的端口号

netstat -a4un //查看UDP端口

netstat -a4tn //查看TCP端口

$ netstat -a4un
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
udp        0      0 0.0.0.0:37745           0.0.0.0:*
udp        0      0 0.0.0.0:5353            0.0.0.0:*
udp        0      0 0.0.0.0:55408           0.0.0.0:*
udp        0      0 0.0.0.0:48385           0.0.0.0:*
udp        0      0 127.0.0.53:53           0.0.0.0:*
udp        0      0 0.0.0.0:69              0.0.0.0:*
udp        0      0 0.0.0.0:111             0.0.0.0:*
udp        0      0 0.0.0.0:620             0.0.0.0:*
udp        0      0 0.0.0.0:631             0.0.0.0:*
udp        0      0 0.0.0.0:59068           0.0.0.0:*
udp        0      0 192.168.0.11:9990       192.168.0.3:37143       ESTABLISHED
udp        0      0 0.0.0.0:42876           0.0.0.0:*
udp        0      0 0.0.0.0:2049            0.0.0.0:*

$ netstat -a4tn
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 127.0.0.1:6010          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:6011          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:6012          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:6013          0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:56063           0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:2049            0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:37699           0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:37195           0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:48533           0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN
tcp        0      0 192.168.0.11:22         192.168.0.5:60730       ESTABLISHED
tcp        0      0 192.168.0.11:2049       192.168.0.3:730         ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:57805       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:53147       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:57305       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:54349       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:53241       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:60727       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:57306       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:56891       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:54348       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:56892       ESTABLISHED
tcp        0      0 192.168.0.11:22         192.168.0.5:57405       ESTABLISHE

小结